What are the most common causes of Error 27 when trying to connect to a Project Zomboid server?

The most common causes for Project Zomboid Error 27 include: the target server being offline or unreachable, incorrect server IP address or port, local firewall or antivirus software blocking the game's connection, router/network issues on the client's end (e.g., port forwarding problems), server-side firewall blocking connections, or a mismatch in game versions between the client and server. Less often, it can be due to server capacity limits or unstable internet connectivity.