|It's possible that the molex connector connected to the CD/DVD drive is loose or defected.|
Not sure if you want to do this but open up your PC case and have a look at the molex connector that is connected to the CD/DVD drive. Push the molex connector securely into the CD/DVD drive... If it still doesn't open then replace the molex connector with another one which should be supplied by your power supply.
It looks like this:
This link below shows where the molex will be connected. Look at the number 4. Forget about the rest of the numbers.
Tell me what the outcome is.