You may either have a device that was rooted. Which then you can't use reset on until it is unrooted. Or if you did a reset of the device that tries to keep personal data, you may have also kept on the device the original problem. Leading to where you are now.
If it was rooted, you must unroot to be able to use any reset. If it wasn't rooted, the following should reset the device.
NOTE: Doing this will clear 'all' the data on your phone, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the phone.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the phone...
1. Make sure that the phone is actually...