Hi Anh Tran,
This topic is still relevant.
I manage about 75 wordpress sites with MainWP. 50 of them use the Meta Box plugin and extensions.
When i check for plugin updates (with MainWP) i don't get the updates of the extensions. When i go the the WordPress admin from one of that sites i see the extension updates. After that i am checking for updates again with MainWP, then the updates are displayed.
It seems that MainWP can not trigger the extension updates. When I log into the WordPress admin I see the updates.
I'd like to help with a solution to the problem. If you need information or a screenrecording please let me know. I have to visit all WordPress admin panels one by one to update the extensions.