Apple Studio Monitor and using Green Screen

Anyone having trouble getting green screen to work with virtual backgrounds when using Apple Studio Monitor?  My virtual backgrounds kind of work without my green screen, but I get the halo effect.  Any suggestions for enabling green screen? I check the box, but all I see is a green background - not my virtual background.  Running 14"MBP in clamshell mode. Have updated Zoom for M1, and updated firmware on Monitor