I have been trying to start Rhino with a licence key for Rhino 7 trial for Mac, but the licence key is not valid when I enter it on the Zoo cloud when starting Rhino, or when I try to add the licence on my personal account on the web.
That’s probably because you have already had at least one trial period previously and the 90 days have expired. You are not allowed more than one 90 day trial. I’m afraid you must decide to buy a license if you wish to continue using Rhino.