If you log in ant the message "You are not allowed to access this page" is displayed as below, it is most likely due to the wrong details being cached (saved) in your browser application. Clear the cache according to the details below and then restart the browser. The instructions are for Google Chrome. For other browsers please refer to the browser manual.
Instructions - Clear the cache in Chrome
Select the menu (three dots) and then "more tools" and "delete web information" respectively.
Select interval "since the account was created" and "Cached images and files". Then press "Clear"