After upgrading I am unable to modify or create user accounts.
After hitting save, a dialogue box appears at the bottom but contains no text.
In the troubleshooting file the version number shows 1.8.12, but in the web interface it shows 2.0.1.
The version in Troubleshoot is a bug, we will need to investigate that, I’ve logged it here https://github.com/xibosignage/xibo/issues/1799
Regarding User add, what do you have in Password Policy? (CMS Settings -> Users tab)
Could you perhaps try to open dev tools in your browser and see what error you get on the network tab for this request?
It seems to be failed on setting up the new password and checking it against the password policy, however, that seems to be rather odd that you didn’t get any error message in the form itself.