In order for SamCart's integration to work you need to ensure that you're using MemberMouse version 2.2.3-103 or higher. You can follow these instructions for upgrading MemberMouse to the latest version: http://support.membermouse.com/support/solutions/articles/9000020393-manually-upgrading-membermouse
Note: SamCart has developed an integration with MemberMouse, MemberMouse has not developed the integration with SamCart.
What this means for you as a customer, in practice, is that when a member signs up with you, SamCart creates a member account for them in MemberMouse. However, the SamCart plugin takes over the subscription management. There's no payment or billing automation handled on the MemberMouse side, it's all handled by SamCart, so it's important to be aware of how this effects your process. For example, if someone purchases something in SamCart and then cancels their account through MemberMouse, the subscription won't be canceled automatically in SamCart.
In essence, you would only be using MemberMouse for access rights and scheduling of protected content. It also removes MemberMouse's affiliate integration features.
As with all 3rd Party Solution plugins, if you are having difficulty integrating or have questions about how it would work, please contact the 3rd Party service. They created the integration, so they alone understand how it is supposed to operate.