Hi HI John Grogan
I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to accept the answer.
Ask: ResourceOperationFailure: Resource provider [N/A] isn't registered with Subscription [N/A] when deploying AML Prompt Flow endpoint
Solution: The issue is resolved. That you were missing 2 additional resource providers that you didn't have originally registered:
Microsoft.Cdn
Microsoft.PolicyInsights
Once I registered these and re-deployed the flow, the endpoint was created successfully.
If I missed anything please let me know and I'd be happy to add it to my answer, or feel free to comment below with any additional information.
If you have any other questions, please let me know. Thank you again for your time and patience throughout this issue.
Please don’t forget to Accept Answer and Yes for "was this answer helpful" wherever the information provided helps you, this can be beneficial to other community members.
Thank You.