Hi,
Thanks for your effort to provide the details with us, we'll try our best to help you troubleshoot.
With your concern that the SharePoint admin unable to access the SharePoint admin center, we did the test and granted a member with SharePoint admin role, he can access the SharePoint admin center without any problem.
Given this situation, we suggest the user try different browsers or the inPrivate windows mode to check the result again.
To continue narrowing down, could you please provide the below information?
- Do other users who have the SharePoint admin role cannot access SharePoint admin center? Please check with other users.
- Please provide the screenshot of the error message.
- When did the issue happen?
Welcome to share any information with us, we will further investigate it. 😊
Best regards,
Gloria