I'm going to ask a question of the OP here but I don't want it taken as being condescending to the OP.
The mini USB plug has a subtle isosceles shape that can sometimes be hard to see. It needs to be plugged in properly to match the shape. Are you sure you are not trying to plug it in upside down? I myself have accidentally made attempts to plug in the cable with the wrong side up/down.
The mini USB cables are pretty common and you might have others laying around the house. If you do, try a different one. Maybe the one you have is slightly bent.
Again, not trying to be condescending - rather offering a thought just to be sure.