The server you are attempting to play on is running an older version of the game.

[ZERO]

Servers updating, should take an hour tops.

---------- Post added at 02:30 PM ---------- Previous post was at 02:28 PM ----------

BTW the reason for the update is a lie this is why:

Counter-Strike: Source
Happy Camper - Get 2 kills standing in the same spot with a zoomed sniper rifle