the problem in my case and perhaps many is that the sim tray is badly designed it’s too deep between the sim and connectors so it’s not flush on the connection side, that minute gap stops it being read, the sim has a spacer around it so when its partly inserted gently push down so it drops, you’ll hear a click it’s still in the spacer but with a better connection, it worked then stopped so i opened it half way and pushed again, it’s now fully connected, this is an old question but still needed an answer for my old phone i’d given up on….
to viswanath, look on the side of the playbook at the charger port, no need to take it apart, use a magnifier if needed check the middle bar in the port is straight not bent.....if it is bent gently level it with a flat thin narrow blade ie metal nail file....when you put the micro charger lead in make sure the blackberry "symbol" on the plastic head of it is facing up..... it will not charge it the other way as I found out the hard way.......hope that helps...