Incorrect track version for your car mod. Some tracks are built for "rFactor 1" but use a physics engine mismatch. Fix: In the track’s .gdb file (open with Notepad), look for TerrainDataFile . If it points to a missing .tdf file, you may need to find an updated version or copy a default terrain file from another track.
Inside the main directory, you will see a folder named GameData . Open it. Rfactor Tracks Download
If you are joining an online league, check their specific Discord or website. Most leagues provide a single Track Pack Incorrect track version for your car mod