Thank you for posting this in Microsoft Q&A.
As I understand you have Global admin role assigned for your account for your tenant and you are unable to access anything in Azure.
When you try to access IAM you are getting permission error.
If you have a Global admin role assigned, this means you are complete admin in Entra ID within Azure. Entra ID is a directory within Azure. With Global admin permissions you can perform anything within the directory like, created users, deleting users, password resets, registering applications etc.
With Global admin role assigned you cannot perform anything within Azure other than within Entra ID.
If you want to perform anything with respect to subscription or resources in Azure then you need to have an IAM role assigned. Example roles, Owner, contributor, User access administrator etc.
You can go through below article to get more information on in-built role in Azure IAM,
https://learn.microsoft.com/en-us/azure/role-based-access-control/built-in-roles
There are multiple roles within Azure with permission defined that will allow you to perform different actions on multiple other resources.
As explained earlier, Azure roles are completely different from Entra ID roles. Global admin is a role which is part of Entra ID.
Let me know if you have any further questions.
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