I have figured out a short term solution to this issue for anyone else experiencing, it’s because of the Firewall on my router (BT Home Hub 6 - UK) i have the default settings on which has always been like this and has worked fine for well decades of gaming, inside my firewalls settings there is also UPnP which is switched ON and underneath that “UPnP extended security” which is also on… like it always has been, now turning the firewall completely off works and i can join anyone in game BUT this leaves your router open to attacks and viruses to your devices (not ideal) …. But if you turn OFF the extended security on the UPnP settings this then allows (at least myself) to join and play with others in the game once again, i’m not sure what’s going on with Bungie and all of a sudden the Universal Plug & Play system built into probably a lot of peoples routers but this firewall feature is what’s making the “NAT TYPE 2” error message appear on screen in game and literally making your router BLOCK anything the game tries to do with matchmaking and joining any players/lobbies it see’s as a potential online threat to the network, to access this you will need to log into your Hub/routers Admin access point and password- this is usually located on your hub/router, find the Firewall settings- if you have UPnP activated leave that on- and turn OFF the extended UPnP security feature and you’ll resume normal gameplay until this is resolved (not even sure if Bungie know this as i have spent hours trying to port-forward and messing around with the Firewall until I realised what would work and wouldn’t work in game)—- side note leave the routers main firewall active/on whatever settings it was originally on for myself this was set to “Default” making sure you are still protected while online with any of your connected devices browsing and using the internet.