Update:
So, in Display (with Windows 10), I changed the "size of text, apps, and other items" from 150% to 125%. This allowed me to view a green log in button at the same time as a green update button. Instead of updating first, I logged in and then updated. I am able to use Bandlab Assistant now.
Explanation of problem:
I think that the Bandlab Assistant page was being cut off and the green update button was covering the green log in button. I am still not sure why I wasn't able to log in after updating (and not before which worked), but oh well.
Brendan's post in Bandlab Assistant not Working was marked as the answer