Ettanin: I got the game on Steam, but I still encountered the issue and figured it would help if I post here because this issue is much more common with GOG than it is with Steam.

Steam users usually won't encounter this issue because Steam offers TURN relays (Steam Datagram Relay). BG3 is a peer-to-peer game and doesn't support IPv6. Therefore, for GOG connectivity to work, either the host or all non-Steam clients must have a dedicated (also called public) IPv4 address. Connectivity will not work if both sides are behind a CGNAT or Dual Stack Lite.

If you got a dedicated IPv4 address, you will need the following ports: UDP 23243 - 23262.
You don't need to forward them if your router is UPnP capable (BG3 will do it for you), but you will have to unblock them in your firewall if you use a firewall.

Alternatives to obtaining a dedicated IPv4 address are either getting the game on Steam or using a VPN server with port forwarding (same ports) or using a virtual LAN tunneling solution such as ZeroTier (in that case, use the ZeroTier LAN IP of the host instead of a Direct Connect ID as the ID to enter).

MaciejSibila: Ok so how to do it?
Im just a regular gamer ant i expeckt it to work plis help

Ettanin: Solution 1: Buy on Steam. Obvious how. Your friends have to, as well.
Solution 2: Ask your provider to take you out of CGNAT or to give you a public IPv4 address. Usually, BG3 will configure port forwarding for you temporarily once you obtained that.
Solution 3: Use services like Hamachi or ZeroTier with your friends. If you do that, simply enter the LAN IPv4 address provided by such service of the host as the direct connection code.

Pick one. Any of them fixes NP66.

ussnorway: unless you are playing Gog vs Gog don't bother

MaciejSibila: Ok now after all that next day i got natpunch 62 insted ^^