Cd | Key Authentication Invalid For Internet Servers Counter Strike Source

: Sometimes the issue is on Valve's end. If the steps above don't work, wait 15–30 minutes to see if the authentication servers stabilize.

Here is a breakdown of what this error means, why it happens, and the context behind it. : Sometimes the issue is on Valve's end

Your Steam account does not own a valid Counter-Strike: Source license for the version you’re trying to play. This usually happens with old retail (disc) keys or third-party keys. why it happens