Hi @Len Ott
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.
Issue:
Azure Key Vault Firewall not working as expected for Azure Services. If you add the IP address of the app service, it can access the key Vault, but without IP address that it cannot.
Solution:
The issue is fixed by connecting the VPN to app service to the key Vault.
If you have any other questions or are still running into more issues, please let me know. Thank you again for your time and patience throughout this issue.
Please remember to "Accept Answer" if any answer/reply helped, so that others in the community facing similar issues can easily find the solution.