Posting this on behalf of another player from Discord, who has this issue every time they try to connect or join a match.
They've tried disabling Windows' Firewall, and double checking the game is allowed access. (Doesn't use an anti-virus program)
"Yes but I checked and it has allowed both Steam and Verdun on both types of networks (I just use Windows Firewall) and when I disabled it, it still couldn't connect. Furthermore I have tried to reach the servers via the Verdun Beta online but it also couldn't connect."
VerdunClientTimeout.PCAP (Google Drive)
Not sure if they have tried the latest update, but I can ask tomorrow on Discord. (Eric Clapton#3158)
Customer support service by UserEcho