HQ will allow any email address to "login", but in order to see the HQ menu and agency information, you must login using the email address that the invite was sent to (and the invite needs to first be accepted!).
If you login to HQ and only see Resources, GloveBox University, and the Dispatch chat icon, logout and verify the email that you are using to login. If you are using the correct email address that is associated with your agency's HQ, but you are still not seeing any agency information, please check with an owner/admin to confirm that your email invited was successfully accepted. If your invite has expired, it will need to be sent again before you are able to successfully access HQ.