So leave it to the kids................ my 3 year old realized i was trying to install upside down. (not really that clear in the picture) and viola! they both work......
I did wonder if you were trying to put it in wrong, but didn't want to say.
I've occasionally had pieces on figures that didn't click into place properly (headwear, for example), but never came across such a problem putting together a vehicle or building.
Speaking of constructing stuff, it took me almost 2 hours to put together the Pyramid on Christmas Day.
Would have been quicker but I overlooked installing a small part which was crucial to making one of the trapdoors work.
I had to pull apart what I'd already built and start again. There are also a lot of stickers and I'm fussy about placement, so I took my time applying them. The end result, however, is brilliant and well worth the money spent.