CSP sometimes caches your game version incorrectly.
The error "Assetto Corsa is obsolete" is a . It appears when the version of your game executable ( assettocorsa.exe ) does not match the version expected by the mod or server you are trying to run. assetto corsa is obsolete v1.16.3 is required fix
Wait for Steam to scan. It will likely find 2–3 files that need re-downloading. This usually forces the game back to the true v1.16.3 state. The Content Manager Bypass CSP sometimes caches your game version incorrectly