Hi @myra18947058anpw, can you describe the problem further or show us a screenshot of what you are looking at? Which “button” isn't clickable? The “Play” arrow on the Timeline? The arrow turns to a square during play. Is the layer selected? When you open a video file from Photoshop (e.g., File > Open > .mp4), the timeline bar should automatically launch with the Play arrow active. Are you opening with that method, or are you using File > Import > Video Frames to Layers?
Just double-checking, you have a document open, correct?
If you happen to be using an older version of Photoshop running on Apple Silicon, you may need to launch Photoshop using Rosetta - but if this is the case it would be better to upgrade to a newer version that runs native on an M1 or M2.