What's the possible problem

Don't assume the battery is good because some lights or radio comes on. A battery with a dead cell can still power those, but not come close to being able to crank the starter motor. Have it tested under load, especially if it's near it's the end of its warranty. You can also try jumping the vehicle from a jump pack or jumper cables and see if that does anything. Check all the battery connections, good and tight. Then move on to things like the starter relay and the rest of the starter circuit and/or ignition circuit.