By default, MainWP should support all premium plugins that use standard WP updates API. However, in case some authors decide to build a custom Update API, it is possible it will cause compatibility issues.
In order to enhance compatibility, we have a custom filter in the place where you can list plugins that MainWP doesn’t see available updates for. It’s documented here.
If that doesn’t help, please feel free to open a helpdesk ticket so we can take a look, but as I mentioned earlier, in some cases, depending on the Update API, there might be no way to make it fully compatible.