I'm using a Mac Mini (M1) with the latest version of Big Sur and the latest version of PhotoShop and I cannot get an assigned keys to run an action. Is this a problem with the Apple Silicon incompatibility?
I'm not able to repro. I assigned "F9" to an action and hit the Fn key + the F9 key and it played. Are you using the Fn/Function key in conjunction with the F9 key?