TG3482G router is not seeing my NAS, but the connection is still good. What is needed for it to see the device as online?

I have a NAS set with a static IP, and am using it to store video, music, and recordings.

I'm having trouble using Port Forwarding with the TG3482G modem/router, as it's done through the XFinity App - and the app does not always see the NAS as 'connected'.

I previously had this working perfectly fine with a Windows system, but now that I've switched to TrueNAS Scale this has become a problem.

The NAS will show up in the XFinity App *sometimes* - I HAVE been able to establish the Port Forwarding rule, and confirm that it works.

However, something is happening to cause the TrueNAS Scale system to show as 'Not connected' to the router, which means it stops forwarding the port.

This happens regardless of what the TrueNAS Scale system is doing - we have been watching a video off of it, only for the Xfinity app to say it's been not connected for 3 hours.

I've tried telling the NAS via cron job to ping the router directly every 5 minutes, via both IP4 and IP6 - but this hasn't resolved the issue.

I've moved the physical connection from the switch below the router, to having the NAS plugged directly into the router itself.

I haven't been able to determine what actually *tells* the router that the NAS is connected - it just, sometimes is, and sometimes isn't.