In 95% of cases, the fix is a combination of a router power cycle, an anti-cheat repair, and verifying your game files. The remaining 5% are network configuration issues (port forwarding, IPv6, or VPNs).
This is the most frequent cause of Error Code 4. deadside error code 4
Before you start changing settings on your computer, check if the problem is actually on the developers' end. In 95% of cases, the fix is a