In order to looking into your issue or upgrade you to the latest version we require your Salesforce org login access.

Please follow the instructions in this article to grant login access to your Salesforce org. 

Please note that you need to grant access to "MassMailer, Inc Support" and give the access for 3 days minimum.

Following screenshots may help you as well.

Navigate to your Name or Profile Picture (top right) -> My Settings -> Personal -> Grant User Login Access.