Door Ajar light has been staying on for weeks. Read thread on these forums recommending WD40 as first step. When spraying, the latch dropped downwards. NOW THE DOOR WON'T CLOSE! help please! 2010 F150 Platinum. The affected door is the driver's side back door. thanks!

 

On my older F150, there was a way to manually trip the latch closed when the door was open, which you must have done. But, I could always reopen that latch using either the inside or outside handles.

I wonder if your "child door locks" are activated? I believe this prevents the door from being opened from the inside. Your owner's manual should tell you what to do if that's the case.

- Jack