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Dear DDPF45,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
1, May I know if the SharePoint site you are accessing is from your company site or from any other companies?
2, I am afraid there is no much you can perform from your side as receiver. Please contact the person who shared it with you. You can suggest him to remove your account from the site following steps in Troubleshoot user profile removal issues in SharePoint - SharePoint in Microsoft 365 | Microsoft Learn. Then re-share it again. Please make sure the email is correct. And on your side, please make sure the email he shared with is the same as your log in email.
Your understanding and patience will be highly appreciated.
If there is any misunderstanding, please feel free to correct me.
Have a nice day!
Best regards,