I get always the same disfunction over month!
The plugin is at the latest version.
Error: [fs_unavailable] Could not access filesystem.
Automatic update for pkugin or themes doesen't work, the same to multisite, but the error is official known and fixed by WordPress dev members in version 4.7.
I noted in this thread on WordPress Core, to understand what is general the Problem.
This problem prevented always updates for plugin after the first item, that means: the first one went through, second once etc. not.
The error I discribed above, is simillar. No update possible for WPMU extensions, but the update mechanism worked basically not. Only manually and that is not ok!
I use "Easy Update Manager" for WordPress instances and the plug works, but WPMU extensions not.
Have you any idea to fix them?