It means that port 6346 which LW uses by default to connect thru is being blocked. "If" the only thing that's changed is your ISP (internet service provider), then perhaps that's the reason. Are you sure you're using the exact same equipment & settings as before?

What you could try is connecting thru another port. You'll need to go to LW's menu bar, Tools>Options>Advanced>Firewalls & change the listening port to another. I'm not sure how you change UPnP port. You may need to close LW after the change. Here's a list of several to try: 1111, 3500, 4008, 1203, 10000, 15189, 80, 20282, 22817, 443, 427, 34599, 40475, 64049.

There's 2 port options. One is listening port, the other is connection port. If possible try to change the connection port. I don't have a UPnP capable router so I'm not sure about whether it's possible to change the port for this or not.

Else manually port forward (prolly the netgear) in order to connect thru other ports.

BTW I'm very grateful you looked around at other posts & did some homework. Thank you for giving the appropriate info without us needing to ask for it.