For Internet Servers Counter Strike Source - Cd Key Authentication Invalid

I know this is an old error, but I just ran into it after digging out my old copy of CS:S, and it took me an hour to fix. If you’re getting when trying to join internet servers (but LAN works fine), here’s what’s actually happening and how to solve it.

If you are seeing this error today, it usually means your Steam client is offline, the game files are corrupted, or the server you are trying to join is running an outdated or incompatible authentication protocol. I know this is an old error, but

Are you getting this error while , or does it happen for every server you try to enter? Are you getting this error while , or

: Deleting the local cache forces Steam to re-authenticate your account credentials. Completely shut down Steam. Are you getting this error while