Hi. Like user4036, I, too, have lost contact with my hub. The hub continues to function, as existing automations are running fine, but I cannot contact the hub by any means. Here are the "did-I-tries":
I tried reseating the Ethernet cable.
I tried powering-down the hub, waiting for any caps to drain, and powered it back up. At this point, the automations started working again, so I know the hub is functioning.
I assumed that it might be a network problem, but my router said it was active (at least at that point; it no longer appears to be).
I moved the hub to the room across the hall which houses my main router. I connected it using a known good whip (which worked fine with other devices), but the symptoms are the same (automations still work, timeout contacting the hub on the LAN).
I went to my.harmony.com and it could no longer find my hub.
The last time the hub made contact, apparently, was just over four hours ago. At that time, I was sitting in a chair, reading a novel, not touching a thing.
Happily, I have a C-7 waiting to set-up and I have a good backup of my failing C-5, but the fact that mine just stopped communicating might have something to do, I suppose, with the recent flurry of updates. As you can see, I'm on 2.3.4.130 (or, at least, I was before the current issue).
Meanwhile, overnight, without changing a thing, it started working again. I hate this sort of issue as there's never 100% certainty. I'll just take it as a wake-up call to finally upgrade to my C-7 which has been waiting patiently in its box. I forgot to mention before that when I moved it to be close to the router, a Synology RT2600ac, I watched the router's light associated with the port come on, which indicates at least nominal health of the connection.
So, I'll assume that it was just a bizarre issue with the router, which had just been updated to a new build a couple of days ago. I'm going to move it back to the other room, and its much longer cable run, and will wait for it to happen again. If it does, this time I'll reboot the router before I try anything else.
In order to find out what IP address your Hub is on, if the standard ways (find....) don't work, use a network scanner. These programs will scan your network looking for open ports. Your Hubitat will have a number of open ports, especially 8081.
If you're using windows, there is Angry IP Scanner.
If you're using Android, there is "Network Scanner".
These will scan all IP ports on your system, and your Hubitat will be evident.
Don't use network reset trick, unless this doesn't work.
