That's because the trailer you loaded don't have any functions, they are like that and will stay like that forever.
But I downloaded it from official mod page, and they are was working before some moment. I just don't know, what happened...
I am going to take a look in a few hours when I have my PC ready (actually when I want to go out of bed )
When I try to use the tanker with the dolly, the dolly either won't turn or it just detaches shortly after starting to drive away. On the dryvan trailer, the dolly seems to get stuck on the trailer while turning sometimes.
I have custom configs for the dryvan and tanker, but they are not included in this mod but in my semi mod... (also updated) The trailers should have custom keys, looking at review vids on youtube it should be working. Anyone not having those keys might have interfering other mods? Might there be an old version installed?
When I turned right, tanker dolly did detach, but I'm not sure if that is hitting L to attach trailer to truck, because I don't think such has happened when I have selected attach all from the menu instead. When I attach that 11 000l petroleum trailer with a dolly to dryvan T75 loaded with Tasti cola, truck pulls quite bit to left at speed. Logging truck with 5 logs seems to be bit unstable, shakes quite a bit after spawning until something brakes and it settles down then. But trailers are really great most of the time, those are only issues I have had, most of the time they work fine and are great fun, these bring a lot into game. I kinda would like to pull 25600kg tasticola trailer with a T75 truck loaded with tasti cola, that would have devastating destructive force, not that currently available combos would not get the job done, but little boy in me would like to have even more destruction
The Small Flat Bed Double U- dont know what the u is for but must be something about the double axles
You have to select the gooseneck hitch on the D-series bed accessories or download AR126B's H-series mod which adds a gooseneck hitch to the H-series.