Hi @Mohaemen ,
I understand you created a user with Global Admin permission and the former work email address. If it is your Azure Tenant and not the company's Azure Tenant which name you have chosen for the UPN (User Principal Name) for this user? It should/could be something like
<name>@<yourtenantname>.onmicrosoft.com . The UPN can be used to login with the corresponding password.
After success you can apply the Global Admin role to your other/new user.
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