I have been trying to figure this out on my own but have had no luck.
When I go into multiplayer I got to user name and password to unlock it begins to go through but after that it pops up saying unlock error in the chat window it say unlock error one. So far I have shut off windows firewall while attempting to unlock, I have tried it on two different computer with the same results. I have only unlocked LFS once and that is on the computer I purchased it with. I can connect to demo servers so there is no problem connecting that I can find, any help would be appreciated!!

Try following the advice in this thread.

If that doesn't sort it out, email the devs.

Thank you for your help I just posted on that thread I hope they can help.

Are you using the right password? You could be using the WEBpassword instead of the GAMEpassword.

Try re-installing the game just in-case it's bugged out.

I changed the password twice just to make sure it will say something different if I do not enter the right password. And I have tried it on two different computers so I do not see how it could be the installation. The weirdest thing about it is that I can connect and get on the demo servers. So I can connect to the master server it just wont unlock.

Doesn't unlocking LFS require different ports than the ones required to play online? You could try opening all outbound ports on your router, as the NAT protection thing (or whatever it's called, I get confused) is basically the only firewall you'll ever need. Failing that, double check and make sure LFS.exe is granted all permissions on all AV and Firewall (manually check in Windows Firewall, even if it's off)

I just double checked windows firewall I am running on a dial-up set up right now so a router would be in the equation I dont want to play online I Just want to unlock so I cn get the other cars and play with LFSTweak