mysfa registration

I registered for a fall class back in the spring semester that didn't have an assigned professor, and now that I have an assigned professor, I'm trying to drop those classes to re-register for the same classes but with a different professor. But when I go to register, it's stuck on terms open for registration, and then it loads, and I get the same error: An error has occurred and your registration cannot be processed.

I've tried on multiple devices and am given this same error message.