Log In
In order for Mansur-Rig toolset to work properly, you must be logged in using an account connected to an active subscription.
In case you haven't already, please visit Mansur-Rig.com to create an account and subscribe to a plan of your choosing.
Once you have an account and an active subscription, you will be able to successfully log-in and activate the product.
To do so, please open My-Account dialog via Mansur-Rig's main menu:

How to use My-Account
Auto-log-in
Once you entered your credentials and successfully activated the product, your credentials will be saved and the product will be activated automatically when you restart Maya. If that isn't your preference, feel free to disable this behavior using Mansur-Rig's Preferences dialog.
Using a multi-seat subscription
In case you have a multi-seat subscription, a few more features will be of your interest.
Logging in with multiple machines at the same time
Managing Users
In case you have multiple machines, your credentials can be used in two ways:
In case you own a multi-seat subscription, you might be interested in allowing multiple users, who are not yourself, to use your subscription (a member of your team most-likely).
In case you don't want to give your full credentials which can be used to do actions within your account, you can alternatively use the User Password field of your account.
This field can be edited via Mansur-Rig's website, in My-Profile section.
Now, the user you want to give access to your account can log-in as a User, which will give him "read-only" access to your account.
You, as an Admin are able to control access to your account, and even force log-out any user using the Manage-Users section in My-Account dialog:
Logging in with different machines
In case you have a single seat subscription and wish to use it on different machines (i.e Home, Office), you are welcome to do so.
If in any case you did not log-out a machine, and want to use a second one, you can always log-out machines as an Admin remotely in order to release the seat using Manage-Users section in My-Account dialog.