It is possible that the problem is related to an updating at the Angelus Press website that has made the site incompatible with the Firefox browser, especially if your computer is running Windows 7 or an even earlier OS, such as XP. If that is the case, try switching to a simpler browser with wider compatibility. Pale Moon is a good choice, and it requires almost no hard drive space whatsoever. If you use Windows 8 or 10, the problem is still probably browser-linked, but your alternatives are greater. I like Opera, which has excellent safeguards and unlike Firefox, keeps adware and bloatware out of your computer. If I were you, I would avoid Internet Explorer and Microsoft Edge on general principles.
If all else fails, try sending a private message either to Matthew or to the CI member AlligatorDicax. Both are very knowledgeable about all computer-related matters.