I am not a tech guy so I will try my best to explain what I know.
My ethernet to my pc had been working no problems for 2 years, I woke up after a storm and it was displaying 'Unidentified network' on my PC. A third party had setup a SAC 6 Way IR PASS Amplifier when we moved in which gave ethernet to each room for faster speeds than the wireless. I assumed the problem was with the SAC box or one of the wires connecting into the box as other rooms were having the same issue using the ethernet ports.
I found a TP link I used to use at my old house and set that up, and it worked (although the speeds weren't as great) I could at least still work from home. That lasted 1 day until this morning when I'm getting the same unidentifed network with this setup as well. So now I don't think the problem is with the SAC box itself.
I have tried all the solutions that I've found online, really no idea where to go from here. The third person that set it up isn't really around anymore and after phoning BT themselves understandbly they told me they don't really advise using third party stuff/can't help with it.
Presumably you still have an Internet connection.
What are you using the SAC 6 Way IR PASS Amplifier for and how is it providing an Ethernet connection?
On checking it would appear that it is not an Ethernet switch so I cannot understand why you thought this may be causing your issue.
If you have Ethernet ports in various rooms they may be getting fed from an Ethernet switch which in turn is being fed from the BT hub or the ports on the rear of the hub will be feeding the rooms.
To check, locate your BT Hub and look on the rear to see how many Ethernet cables are plugged into the rear ports and check where the Ethernet cable(s) are going.
However before doing that I would suggest that you try a factory reset of the BT hub by pressing a pin into the recess button on the rear for about 20 seconds and once it has restarted check to see if the notification is still there.