I can unlock my 2011 f150 with my remote, however I cannot lock my vehicle.

 

at all?

 

You might want to think about replacing the battery in your FOB. If that doesn't solve it, you'll probably need a new FOB, sounds like the button might be worn out. I have a similar issue, but with my unlock rather than lock. I just keep pushing it until it finally works lol

 

Push the button on the door when you get out?