Just to clarify, were there any changes prior to this issue? Are you an admin or co-admin on the subscription?
--You may need to verify the role assignments for your account.
--If you haven't tried this already so, On Azure Portal > On your profile (you can see the identity you’re using in the upper right-hand side of your Azure portal) >> select
Switch directory . ( screenshot below)
You may change the directory by selecting the Directory and Subscription filter button on the toolbar along the top. Ensure that you are the right directory.
Change Directory Tenants with your Azure Subscriptions
--You may always file a (free) support ticket with our Azure subscription support team create an Azure support request for quick assistance. Select Subscription Management for the issue type.
· Checkout this FAQ: How do I submit a support request if I can't sign in to the Azure portal?
· Call the customer service number for your country/region.
You have posted the question on Azure App Service tag, we may need to re-tag appropriately to receive insights from the targetted audience/SMEs.