@KEMS KEMS Thanks for reaching here as suggested here- https://learn.microsoft.com/en-us/answers/questions/1657059/the-subscription-is-not-allowed-to-create-or-updat, try the following:
- Retry to provision the App Service after a few hours
- If your requirement fits, try deploying in a different region.
- If you continue to receive this error, please raise a a support ticket for a closer investigation.
Users with a similar issue, resolved with the suggestions provided.