Hi @Michael Agbogidi 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 .
Error Message:
Access to 'https://dms-dev-app-config.azconfig.io/kv?key=ConnectionStrings%3AAppConfig&label=%00&api-version=1.0' was denied. Please ensure the required role assignment is made for the identity running this task.
Issue:
Service connection from Azure Devops to the portal failed after key renewal even after confirming that the creator of the service connection has the owner role as well as the App Configuration Data Reader role.
Solution:
Assigning App Configuration Data Reader Role to the app helped resolve the issue.
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.
I hope this helps!
If you have any other questions, please let me know. Thank you again for your time and patience throughout this issue.