The 'Access Denied' error is generated when a User attempts to access a Module they do not have privileges for.

If you are receiving this error on initial login, you do not have privileges to the Default Module assigned to your User login. For assistance updating your Module Privileges or Default Module, please contact your Superadmins.

Any Modules you do have privileges for will still be accessible through the waffle menu when receiving the 'Access Denied' error.