My server disappears after the NAS restarts
The server is fine. Its media device is still registering while the library scan runs.
If your NAS powers down at night, this is the normal morning state and not a fault.
When MinimServer starts it comes up in stages. Its monitor service registers on the network immediately, but the media server device itself only appears once the library scan has finished. On a large library that can take several minutes. In that window the server is running, answering on the network, and still unable to serve a single browse request.
Serento recognises this. You will see "Almost ready: your server is still loading its library" rather than an error, and the app keeps watching in the background. When the media device registers, the connection re-binds itself and the page reloads on its own. You do not need to restart anything, re-add the server, or force a sync.
If it is still saying that after fifteen or twenty minutes, check MinimServer's own status page: a scan that never completes usually means it is stuck on a folder it cannot read.
Still stuck
Write to us with your server, your streamer and what you expected to happen. If you can, send the diagnostic log from Settings, it usually answers the question faster than a description can.