I bought my 2010 Superduty new. It has a tailgate step.
Not too long after owning it, I tried to open the tailgate and it would not open. The handle would pull up, but the gate would not release and open. I gave up and went into the house. I came out later to mess with it and finally got it down. As time went on, it happened more and more frequently. I took it to the dealer and told them that is seemed to do it only when it was not parked on level ground and then not all the time. I noticed that when I would try it and it would not open, I could push it shut and hear it latch, then if I would push the step down and then retry to open it, it sometimes opened.
The dealer said he found no problem. I would bet he pulled it into the garage and it worked fine. They really seemed like they could care less.
Well I put a cover on my bed and with the cover on if it does not open it is very hard to do. If you have something in the bed that you need it is very irritating. Now, it has gotten worse. It seems like it needs an adjustment>
Anyone have that problem?

 

Honestly, not sure if this will be of any help at all, as you're a full decade newer than mine, but I just addressed a very similar issue on my '99.

I dropped the tailgate, and pulled out the 8(?) torx screws, revealing the mechanism for the release handle inside. I sprayed a good amount of white lithium grease on all hinging parts, sliding parts, springs, key holes ... everything that moved (even some that didn't). I also lubed up the pins that it latches on to, as well as the locking tabs that hold on to the pins in the bed.

Bolted 'er back up, and it's now like butter, unlatches every time with a single finger.

Like I said, not sure if it's equivalent, but that's my experience.

 

I thought of that, but woulda thought since I bought it new that might not be it. But you know what, all that will cost me is a little lube and time. I think I will do that. I might wait until it warms up about 20 degs. first. Maybe I will even see some type of adjustment or even see what is not happening. Great idea thanks. I just thought of something. I have a sprayed on bedliner and wonder if I can access the bolts to the tailgate panel? I cannot remember without looking at it. I also wonder now if that is not what somehow caused the problem in the first place, but if that were so, why would pushing the step down on the tailgate affect that?

 

Yeah, I'm not sure on the bedliner. Mine was sprayed in too, but they removed the bolts first so they were accessible and not full of bedliner material. Here's hoping yours is the same!

I'm not sure how the mechanisms are different, but mine lacked most adjustability. A bit in overall length, but nothing that needed tweaking (and I thought there would be need for adjustment, it was really sloppy). It was amazed how big a difference a little grease made.

Good luck!