I think there’s some other posts on here about py2/3 issues, sounds like you’ll need to delete (or the safer option of renaming) the local user Thinkbox folder
C:\Users\USERNAME\AppData\Local\Thinkbox
What’s the issue with Houdini 19? There’s a very old thread requesting 19 support
worth reading through and adding your voice there, may get an update in time for 19.5 launch