Hello @Winitr (MIS) Montewan
Based on the description you have added the user as owner in IAM. but unfortunately, the user cannot access the resource and got error as shown in the screenshot
Verify the role assignment is the user has listed in owner list. Sometimes role assignment will take 10 minutes to effect. If the assignment was just made, wait a few minutes and ask the user to sign out and sign in again.
Make sure the user is logging in to the correct Microsoft Entra ID tenant. If your organization has multiple tenants, verify that the user is in the same directory as the subscription.
Ensure there are no policies blocking access for this user like Conditional access policy
Sometimes cached credentials cause issues. Ask the user to try accessing the portal from an incognito/private window. Ensure the subscription is active and not disabled or in a suspended state
Please follow the steps above and let me know which step resolves the issue or if you need further assistance please click "Comment".
I hope this information is helpful. Please feel free to reach out if you have any further questions.
If the answer is helpful, please click "Accept Answer"
and kindly upvote it.