Something is stopping it from going all the way in
The cup hitting the spacer thing in the middle?(something bent or not compatible)
The edge of the bb shell not ‘faced’ (build up of paint, etc) 2 mm? Hmmm.
The BB threads being blocked at some point - chase them out.
The bb shell width incompatible (68 vs 73) already discounted.
If you file or cut some of the threads away, it might work - but what is the problem you’re fixing? BBs don’t usually need such attention. I’d need to know the reason.
The first thing I'd do in this case is chase the BB shell threads but then I have easy access to the bloody expensive tool for doing so. The trouble with filing the thread on the actual BB is that if the start of the thread ends up less than perfect you run the risk of making a complete mess of the thread in the frame. I'd take it to a shop and have it faced and chased.