I moved your post since the original post was a bit old, versions might be different and the underlying problem might be different as well.
So the first day it was working?
Does it work for 1 account, and 1 user? With/without app password? Login on web-interface works I suppose.
You need to narrow down the problem, is this problem because of using multiple accounts, or is it already not working for a single one. Is it just the desktop client, or a more general problem.
When you open a new issue, there is normally a support template: Support template. Please use this when you request support
Some of the information might be helpful, e.g. if you use an external authentication backend etc. Logfiles might be helpful as well.
Well, for many it seems to be working.