In order to fix Engine Error: Library Client (Could not load library client) in Left 4 Dead 2, you can try these;
- Go to Steam and verify Left 4 Dead 2 game files.
- Open Windows explorer and go to the installation folder of Left 4 Dead.
- Navigate to L4D2Directory > Left 4 Dead 2 > left4dead2 > bin.
- Look for “client.dll“.
- Go to its Properties and set its permissions to “read-only” mode.
- Launch Left 4 Dead 2.
Enjoy your game 🙂