I hope you resolve this to the state of ready and working mod (but what are you doing ?? laser rangefinder in a Panther ??) and then you let to take me a look, because I would like some new keys too in AB (like start/stop engine, maybe change gears, some new gunsight options ect, some new secret funtion
...) but lately never had enough time/patience to learn from the begining how key interactions work in Unreal...
P.S. Anyway, I see few problems in it. First you tried to make AddInteraction within PostBeginPlay (although it was said to not do it) and in your button class instead of playercontroller class (so hmm an ROPlayer ?). Maybe it has to be added by mutator...
Third problem with Begin was that it should be put into correct place inside "state PlayerWaiting" (not sure if state can be extended in subclasses ?) in PlayerController class (or it's subclasss?) and not just written without context (and not in your button class anyway).
As I'm not sure how to modify RoPlayer class (I thought for a moment that ROTankCannonPawn is subclass of it, but not) then the only way to put this interaxction into the game would be by mutator - I think (I can be wrong of course). So totally different way.
Maybe remove AddInteraction part from your button (this one for sure) and put it into your mutator (if you have one).
Are my comments making any sense ?? Worluk ?
edit: I see that states can be extended... but not from subclasses ? So better get rid of this and make AddInteraction by mutator I believe ? We don't have acces to ROPlayer or PlayerController anyway from tank/CannonPawn classes. But I'm not too happy that I need the mutator to get the additional key interactions working, I would prefer to get this from inside the vehicle/base vehicle code to be mutator - independent... Well you can't have everything I guess...