Thank you for posting your query on Q&A.
I understand that you are trying to service principal and you have got the error message stating insufficient privileges.
It's seems the account you’re using does not have the necessary permissions to create the service principal.
To create the service principal, you need Global Administrator or least Application Developer or User Access Administrator Role. could you please check that?
I hope this information helps! please Feel free to ask any questions you may have.
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