Here’s the most common source of confusion: a few years ago, after official development on Assetto Corsa had stopped, . This update didn't change anything visible to the player, but it altered that changelog.txt file, changing the version number. At the time, older versions of CSP had not been updated to recognize this new version, v1.16.4. Consequently, CSP saw the string "v1.16.4," didn't know what it was, and defaulted to assuming the game was obsolete because it wasn't the version it expected (v1.16.3).

A server requires a specific CSP version that your system is misinterpreting as a base game version error. How to Fix the Error (Step-by-Step) Follow these solutions in order to resolve the issue. 1. Force Steam to Update Assetto Corsa

Launch Assetto Corsa once directly from Steam (not via Content Manager).

You now have all the tools and knowledge to resolve it quickly, from the simple "do nothing" approach to editing a file or updating your mods. While there are torrents and unofficial links for v1.16.3 scattered across the internet, these are unnecessary for solving this error. The fixes are already in your hands.

Allow Steam to complete its scans and restore any core deployment missing linkages. Troubleshooting Summary How to update content manager in Assetto Corsa? - Facebook

Sometimes, a mod or a crash can corrupt the version.txt file or the executable, leading the game to report the wrong build number.

However, the “link” refers to community-provided downgrade tools or the direct download of the v1163 executable from trusted sources (which we will discuss legally). In the modding community, the “link” is typically:

CONNECTION FAILED: ASSETTO CORSA IS OBSOLETE. V1163 IS REQUIRED.

Assetto Corsa Is Obsolete: Why V1.16.3 is Required and How to Fix It