This message means you are no-longer connected to any MX customers (you have been removed from the address book). Some customers perform clean-ups of the address books when users have not logged in for some time.
​
You need to speak to your contact at the company who provided you with the MX account and request that you are added back in to MX.

As long as your email address is the same, you will be able to see all of your past activity with that company.