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You need to find a library worker who understands how the computers work.
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Not necessarily (and probably not) a librarian -- they know how to find information and books, and how to organize books.
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The computer tech they use might only be there a few hours each week, so ask to find out when he comes in.
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Be sure you are using a computer set aside for adults, not one for children.
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They might have gotten the children's settings mixed up with adult computers, for example.
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Pay close attention when you select or reserve a computer because you might have picked one for children by mistake.
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If you reserved a computer by way of phone call the library rep (probably not a "librarian") may have chosen a child's computer.
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I have had days when CathInfo was not accessible at the library and then came back another day and it was accessible.
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So I don't have all the answers, but I have found that some libraries have strange filters for whatever reason.
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Perhaps they don't want children or even adults playing games online at the library, and since CI has login and allows contributions of text and lets you see other members' contributions, it might look like a gaming site to a system control robot. Only a knowledgeable computer technician would understand that, though.
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Once you find a system tech who can access system settings, you could request that CathInfo be put on a list of EXCEPTIONS whereby you can use it even when the system IDs it as a site that should be blocked. You can show him for example, that there is nothing on CI that ought to be blocked at the Library.
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I'd say that it could be that CathInfo allows free discussion about things Jєωιѕн.

Or maybe it was the ADL, instead.

Possibly because CI is a forum largely inhabited by SSPX and SSPX resistance trads, and may be banned because of the SPLC report or relationship to +W? Can you access the SSPX site from the library? I know libraries often block sites that aren't politically correct. I hope this isn't the case.

yeh, that was my thought: PC
but I don't really know. I live in a mostly conservative-leaning area but there are libs and other weirdskis all over the place

During the Obama Administration, the obsoletely titled "Southern Poverty" Law Center [†], which promotes itself as a "civil-rights organization", received federal funding to provide "hate-group" training to the (U.S.) Federal Bureau of Investigation!  [....]  At least as long ago as 2006, SPLC began promoting disparaging radical claims about traditional Catholics [....]

Imagine that you are the chief librarian for a city or county library system in the U.S.A.   You're trying not only to maintain existing services, but also provide new services, of which public access to the Internet is increasingly popular.  But because of unrelated demands on the city or county budget [$], the budget assigned to your libraries is merely flat in a favorable year, or progressively reduced in less favorable years.  That's why you got your degrees in Library Science(s), right?   Becoming the administrator whose continued employment depends on providing more & more services--crowding out traditional library services--with less & less total money every year.

Hey!  Soon you won't even need such a big building for the library, and you'll be able to reduce your budget, saving money for the city or county, by downsizing all your building(s).  Because "everyone knows" that soon enough, "all books will be digitized" and "on the Internet".  And numerous debates with your city council or county commission have made it clear that they believe that it's true, and expect you to make it happen--soon.  No matter how patiently you've tried to explain to them, based on your good practical sense, what an impossible--not necessarily even desirable--dream that popular delusion really is.  And in the meantime, your budget no longer allows you to keep even 1 computer or network tech in each of your libraries during all of their open hours.

So once again another school shooting by some teen made national headlines.  And he was soon discovered on social media beforehand, proclaiming his misguided allegiance to some "hate" group--the genuine kind being few and far between--or profoundly embarrassing a legitimate ethnic-heritage group by claiming them as his motivation for his reprehensible acts.  Never mind whether some pediatric-psychiatrist has fried parts of that teen's brain with years of psychoactive drugs before & after puberty (when responses to drugs can dramatically differ).

So parents and the city council or county commission are again demanding that all "hate speech" must be filtered out from the computers in your library system.  Will that council or commission add funds to your budget so you can accomplish that?   What a silly question!   Of course they won't!  But it's been made clear that you'd better find a way to make that filtering happen, and soon!

While you're imagining, please assume that the software in my speculative scenario below actually exists; I don't know that it doesn't, but it fits the modern promiscuous "install our custom app" model about which U.S. sheeple seem to respond "the more, the merrier"!  Never mind that it would enable SPLC to install & enforce its private biases in local-taxpayer-funded public libraries.

Let's imagine that you briefly escape the daily library grind by attending your annual librarians' conference.  You're relieved to have professional time among your own kind, and maybe more so, time away from self-centered parents and local politicians.  But it's soon back to reality, as you discover that SPLC bought its way in to librarians'-conference seminars by paying for a big exhibit booth.  At their seminar, they tell you about their Internet software, which not only will filter out "hate", but also won't cost your libraries even a cent, because they are partnered with your federal government, which is "here to help you",  by paying for everything!   As of a few years ago, SPLC didn't really need donations to meet its expenses (it was already sitting on plenty, but sent out its solicitations anyhow); so what they would've wanted to gain from the federal partnership wouldn't necessarily have been more money, but the official or de facto federal endorsement.  For participation in the conference, SPLC, which must know how skittish librarians can be about the odor of "censorship",  would've scrubbed away as much evidence as possible of their own biases against pride in traditional religion and cultural heritage, so the offer would seem safe, albeit a little too good to be true.

But in your tenure as chief librarian, you've worked too hard to accomplish what you have in your library system, to risk having your career be ruined by being accused of "failure to protect the public".  You know the recurring slogans: "Anything to protect the children",  and all that.  You've been repeatedly assured that the federally funded SPLC-specified software is really free to your entire library system.  You suppose it's at least worth giving it a trial run.  Sigh.  So you go ahead and set an appointment for them to install it.  But even tho' you fail to notice the metaphorical resemblance to a lobster trap, you briefly recall Han Solo and the original film's "little moon": You indeed have "a bad feeling about this" [×].

How long will it take for the realization to dawn on you--and your library staff--that blocking access to CathInfo isn't a bug in the software at all: SPLC probably considers the site to be infested with "radical traditionalist" Catholics, so blocking C.I. would definitely be a feature!

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Note $: E.g., funding new sports venues for billionaire pro-sports franchise owners; bloating the payrolls and squeezing office space in the city or county school system with educrats imposing political correctness; subsidizing hospitals that are legally victimized required to provide free care to unemployed nonresidents (d.b.a. "the homeless") and illegal aliens (mustn't-ask, don't-report).

Note ×: If your budget can't pay for you to install such filtering software, how can your budget pay for you to remove it, if--or when--your "trial run" proves that removal is what's best overall for your library system, hmmm?