What is the button that is two buttons left of the Three Dots button?
This is from a movie card in the Plex for Mac (Intel) 1.41.0. I would assume there would be no difference running the Plex for Mac client on Intel or Apple Silicon at this point.
Are you signed in with your user id in Plex for Mac?
If you are using a Managed Account or Friend login, make sure it has permissions to download media. Also, if using a Friend account, that account must also have a Plex Pass.
Sign out / back in to your account in the Plex for Mac app. The app will have to re-authorize your account with plex.tv, making sure your Plex Pass credentials are picked up and you have permission to download media.