Cannot Connect to Any Servers

[Mondale]

I had to rebuild my PC and restored all my steam files and now CoD4 will load but I get the following error when trying to join any server

"Error
Can not connect to server because the update backend is unavailable
To join this server you have to install the required update manually"

I've tried going to the link but there does't seem to be anything there that's helpful.

I've googled and searched Youtubed the problem and can't seem to find anything that's helpful. Anyone know how to fix this?

[Alptekin]

Same problem. Lots of different solutions in youtube. I got confused.

[Mondale]

I found this video, it worked.

https://www.youtube.com/watch?v=EdOBwcZ_20A