The fact that you are able to log in means that the database is up and running, otherwise you couldn't connect to it.
We did the exact same upgrade and haven't had any issues with upgrading the manager,
This may sound stupid but did you try with another browser?
And regarding the licensing, this is just a key with a specific name that adds a number of users that you can add in Appvolumes. You could download a new license file from the website but to be honest it is no really needed, the name is no indication for the license itself. As long as you see correct info on the dashboard there's no need to worry about the license.
Try to access the AppVol manager window directly from AppVol server and check whether you can able to access. Reset cookies and cache from browser and then try access.
Stop AppVol services from AVM server and login to DB and refresh AppVol DB then try accessing dashboard.
If not then try to check in the logs.