DGN1000 wired connection issue

My mum has one of these and just recently, the wired LAN connection to her desktop PC doesn't seem to want to work. She has an iPad which connects via the router to the internet and is working well, but just can't seem to get the wired connection working. The number 1 light shows green which is where the desktop connects into. My guess is that it is a problem with the computer, but device manager shows the LAN device working ok.

Any thoughts or suggestions on what I can try. I will look at the firewall settings tonight, but my mum lives 5000kms away and is 82, so not that easy to solve over the phone!. Interestingly, I asked my nephew to setup remote access to the router so I could log into it from here, but that doesn't seem to want to work either!