Ok here's a tip for you.Don't spam this question/issue on multiple threads, this is the third thread.Forum members and officials will not take it seriously if people spam it.Just be patient and give it a short while, someone will give you feedback.

I had a similar issue once where my units reached the province center but didn't capture it.I restarted my device and when I got back into the game then only it was captured.
Just confirm if Cuba maybe gave you Right of Way, maybe that's why they don't capture it.If Cuba did you need to declare war on it.

There's also an issue about stealth units. When both sides can't "see" eachother, no combat is initiated, and the province doesn't change hands. The attacker can just wander off on any road. When the defender wanders off, the attacker still takes the province, although I think he needs to initiate some kind of movement for that.