The most common scenario for the "Access Denied" error message is bookmarking the login page rather than being redirected to a login page from the below links. This will cause an access denied error message.
Stage (Test Environment) Portal:
Another common symptom is due to the browser cache, in the case small enhancements are made on our end to improve the user experience, the user may need to refresh their browser cache so that the browser being used can properly cache the latest iteration of the portal. It is recommended to refresh the browser cache regularly.
Last, try logging into the portal from another browser to rule out the root cause being a browser issue.
If you are still experiencing issues logging into the portal, please send an email to support at firstname.lastname@example.org with a brief explanation of your issue and our Client Delivery team will work with you on resolving your issue.