I distinctly remember this being an issue a few versions ago and im almost certain the was a Registry tweak to fix it but I cannot find that from googling now.
The Only one I can find is to create a DWord Regsitry Value in "Computer\HKEY_CURRENT_USER\SOFTWARE\TeamViewer"
Named: OldInsessionUI
Value: 1
However whilst this does change the UI to look like the old UI it doesnt fix Autotype sadly.
I am almost certain there is a Regkey to fix as Ive just swapped to a new Laptop and it was working on my old Laptop which sadly died but even with the Latest TeamViewer and latest In Session UI KeePass Autotype worked.
It seems that KeePass cant take the Window Focus away from TeamViewer so you run AutoType and it grabs the Window but doesnt follow the field your cursor is in but rather is stuck in the Actual TeamViewer context menu's themselves inside the interface.
This has absolutely killed productivity as we have Passwords that are sometimes in Excess of 20 Characters which can now no longer be typed in at the Login Screen, or Windows Password prompts and Copy/Paste isnt available for these Windows making Autotype via Keepass the only option other than to manually type crazy long passwords each time.