Can't register all Acrobat installs at website, and some installs require site login, and other mysteries

Over the past 4 years, I've bought 16 Acrobat licenses through TechSoup. I have a single Adobe login and I've only been able to register 4 serial numbers through it. When I try to register more, it tells me, "An error appeared while registering your product". Plus, some users get a popup when using it telling them to sign into the registration website and when they do, they can use Acrobat, even though it's not registered there. How do I fix this?