Hi otwcaravan,
Based on your description, I understand that you have been encountering the issue that the error message “Sorry! We can't process your request right now. You don’t have permission to access this page or perform this action.” occurred when signing in your Team Site in Office 365 Portal.
This may be caused by lacking the permission, to solve the issue, please following the steps below:
1. Log in to the Microsoft Online Portal with the admin account.
2. Click “Team Site” on the top of the Admin page.
3. Click “Site Action” dropdown list and select “Site Settings”.
4. Click “People and groups” under “Users and Permissions”.
5. Add your account to the proper group in order to give permission to the account.
Thanks,
Allen Zhang