Protocol 21 not working

Okay hello guys i have a problem whenever i download a protocol21 and do the following stuff like running it and then when i press on COd then its like black screen and says input not connected how to fix plz guys plz

Ok off your description not 100% sure what you mean but I assume you haven’t got 21.1 client installed.

Extract it to your cod4 directory eg. C:\Program Files (x86)\Activision\Call of Duty 4 - Modern Warfare
open the cod4x_client_21_1 folder and find install.cmd and run it.

Hope this now fixes your problem