@em1016 led me to a solution.
I’m in the UK - I went to Settings > General > Language & Region and changed the Region (not the language) to United States.
I then opened Playground and it worked.
I then reset the region BACK to United Kingdom and it still worked.
This seems like a bug to me - I wonder if the AI tools are going into an update mode whenever there is an update made to the US model, but it’s doing that worldwide even when the update for your region isn’t there yet, or something isn’t tying up outside the US. It would be interesting if anyone having issues is in the US.
Resetting your phone is not a solution for this problem, it’s just masking a problem that will reappear the next time an updated model shows up.
[Edited by Moderator]