No unfortunately your key will not work for version 3.6 - well, even if you could somehow manage to get your hands on it.
Visionaire Studio 4.x was significantly overhauled from 3.x & besides the engine getting overhauled it came with various new features, the overhauled part of the way some of the old features / systems worked is probably why you are encountering certain bugs where things worked fine in the version you previously had. If you want to upgrade, then you will have to try to iron out the kinks & update things as needed.
I setting the log level inside of Visionaire Studio editors options under extras
to "info". This will record everything to the log including warnings & errors. The messages.log file should probably give you an idea what's causing some of the errors.
If you don't know how to locate your messages.log file then, run your game via the editor, press TAB key to open up the developers console. Now type...
exec print( localAppDir )
now press enter, & then type...
& press enter again & it should overlay the messages log. Navigate through the pages with the page up / down keys on your keyboard until you see a line that contains something along the lines of c:/users/...
, which will be the location where the log files & save game files of your game are being stored.