I tried to edit my previous answer, but again this interface caches things for so long that it won't show it to me.
I see that it's a service endpoint policy that you're having an issue with, not the service endpoint. (Misread that earlier).
If so, that message above clearly just says that you're not authorized to delete the service endpoint policy. This has been reported before, and the response was that you'll need to contact Microsoft support to get it deleted at the backend as it's "stuck": https://learn.microsoft.com/en-us/answers/questions/464085/resource-group-has-a-hidden-service-endpoint-polic
They had exactly the same error (including the typo with "if not authorized" instead of "is not authorized". Wish it was better news.