This is in forum threads here many times, and you’re going to get a lot of suggestions, some of them contradictory. It can be hard to release. Some members have changed their couplers because of it. I have a new coupler for some year when I finally get to it. I have owned many differing trailers, and this is the most obstinate coupler I’ve ever used.
So here’s my take, which some will disagree with. When I’m set to uncouple, I give the trailer a very gentle tug forward and keep it there. Almost always that will allow the latch to be raised. If not, I reluctantly resort to brute force with a pry bay under the collar. It’s not best practice, but it’s got to come off. Fortunately, that’s a rarely employed tactic. Others will suggest allowing the truck to roll a bit or move rearward. That might work for them. For my coupler and ball combination, it’s always forward for both hitching and unhitching that works.
Once the latch is up, I raise the tongue. If it does not come off, which is often the case, I keep cranking the tongue higher until I’m lifting the truck suspension. Then, usually bumping the truck forward will drop it off the ball; however, sometimes at this point shifting to neutral will work. Sometimes I have to crank the truck suspension up pretty hard and now have a 5000lbs tongue jack.
Not that it matters really, but I have a manual tongue jack.
At this point, I’ve always had it release.
One tip that works for me, is when I use my curved levelers, is to pull on them instead of backing on them. That almost always gets the latch up. When I back on, invariably, I have to start by getting the ball forward in the coupler.
My ball is the 2” ball designed for the Equalizer hitch.
Keeping things lubed helps too.