when i reverse onto the pin my handle now doesnt automatically engage, you have to get out and knock the handle across to get it to go in and engage, it worked fine [ only 3 months old] until they broke the shunter and used mine as a shunter for a day, the handles been replaced as the shunters somehow managed to twist it and break the little welded block that stops the last bit of the handle from pivoting on the bolt , its not the end of the world but i just wondered if anyone had a idea as to why it doesnt engage automatically ta
is there any slack in the 5th wheel when you rock the truck after coupling up ?. it may need adjusting. this is the long bolt with a nut on the fifth wheel side. you undo the locking nut then turn the large bolt anti clockwise to adjust. then tighten locking nut.
As Mr. Slicker 
says, reckon either the side bolt or the handle needs adjusting. Same thing happened to our shunter. Pain in the rear knocking it in all day. Workshop adjusted it when we complained, went ok for a few weeks, then put new jaws in, ok for another few weeks, then finally ended up doin a bodge job which has worked the best! When dropping a trailer you obviously pull the handle out, then as you pull off the pin you hear the handle click. This is the sound of it re-setting itself for the next trailer. Don’t know exactly what happens, but what they did on ours was slightly grind down the notch on the handle where it hooks up on the side of the fifth wheel. This means you have to be slightly more careful when pulling the handle out to make sure it stays out, but now we’ve got used to it, it’s fine. Obviously this has made it easier for the handle to lock in when backing onto the pin, first time every time now 
Your fifth wheel being new, it should just need the handle looking at again and a bit of adjusting.
Sorry to go around the houses, hope this helps!
On some 5th wheels, there is a slot in the handle to lock it out. I bet on your old handle it had a wedge shaped piece cut out of its side and this one has a slot…
Slotted handles only need to be locked so you can pull out from under a trailer. Once you are out, the tension in the mechanism keeps the handle out.
Knock the handle across before reversing under your trailer. It will stay out and then drop in and engage the locks automatically, as usual.
(It will probably drop in slightly when you knock it across, 1/2 an inch or so)
If that doesn’t work, r slicker and Roger Breaker are probably right, but my way is easy for you to check.
Don’t adjust anything yourself, get the grease monkeys to do that. That’s what they are trained and payed for. If you get it wrong, you could loose a trailer (not likely, but possible), but if you adjust it yourself and that happens YOU are very deep in the [zb].
It sounds like they changed the handle to a different type all together. Probably still a Jost handle, but for a different 5th wheel model.
It looked almost the same, it fits, it works, we don’t have to muck about with it several times a day, so it’ll be OK then. 