Tailgate won't lock

Hi, I've got a 2004 LS 2WD. Recently the interior lights stay on and I have to hit the manual lock twice for the doors to lock. The remote unlock will not work at all (either lock or unlock). The tailgate and window will not lock even when I hit the manual lock on the driver's door. It seems as though the vehicle is not recognizing that the tailgate is closed (even though it is). I can't find any physical reason the tailgate is not securely closed. Everything else electrically works fine (except the rear wiper - which wouldn't turn on anyway if the vehicle thinks the gate is not closed securely). Has anyone ever seen this or have any suggestions on how to correct? Thanks for your advice.

I have a problem with the window not locking. As for the gate ajar I would get that when I got a lil piece of cloth stuck in the latch on the gate.