After I upgraded my late 2016 MacBook Pro to Catalina (macOS 10.15), I noticed that Window Snapping is no longer working on BTT 3.202. I upgraded to the BTT Alpha (3.204) and experienced the same behavior.
Only after I removed BTT and reinstalled it was I able to get Window Snapping to work.
HOWEVER - after restarting the BTT application, window snapping no longer functions again.
So the scenario seems to be that after a clean install on Catalina, window snapping functions, but if you are to restart the BTT application, window snapping does not function.
I can reproduce this consistently - any help would be much appreciated!