Unable to connect to a friend for co-op play despite trying all known solutions

[Qwart]

Hello everyone,

I'm reaching out because my friend and I have been unable to connect to each other for co-op play (zombies), and we've completely run out of ideas.

Here's what we know and what we've tried so far:

We are both running the same game version and the same launcher version. There are no errors or issues within the launcher itself — everything looks normal. The problem occurs specifically when we attempt to join each other's session. The connection simply fails every time with no clear error message.

Here is a list of everything we have already attempted:

— Tried connecting both with VPN enabled and with VPN disabled. — Tried connecting over a local network using Radmin VPN. — Set up port forwarding on the router for port 3074. — NAT type is showing as Moderate on both ends. — Disabled antivirus software completely. — Disabled Windows Firewall completely.

None of these steps have made any difference. We are stuck and unable to play together regardless of what we try.

[clde]

i had to add the plutonium bootstrapper and launcher exe in appdata/local/plutonium/bin to my firewall rules allowing inbound and outbound connections. I also made sure my network was set to private.