If you own WRC 3 on Steam and get a “serial number required” pop-up:
Because the game has been delisted due to expiring licenses, obtaining a new serial number requires looking at alternative markets: WRC 3 FIA World Rally Championship - Steam Search Wrc 3 Serial Number Pc Games
Even if you have a genuine, unused serial number from a new old-stock DVD: If you own WRC 3 on Steam and
A serial number (or CD key) is a unique alphanumeric code used to activate and verify a legal copy of a game. For WRC 3 , these were originally found: these were originally found: