Hi there !
I have the same issue...My BM ATEM mini pro is not recorgnize by Arena on my macbook M1 (Arena 6.1.2).
But it worked, it's well recognized on my PC with the demo versino of the last Arena 7, so the ATEM is fine.
So I've tried to instal the demo version of Arena 7 on my mac but it doesn't work.. ATEM is not on the sources/capturing devices..
It's very strange, can someone help me ?