When you dropped your phone, did it physically dent it in and it no longer clicks, which is what activates the on/off action, or you just dropped it and although it is in good condition, it will just no longer work? Either way, you may have damaged the flex cable responsible for the power button and it most likely will need to be replaced. However, if the power button is dented inwards, you will need to get a dent remover for your phone (they sell them for iPhone's, but I do not know about the Razer phone) and straighten the dent, then put in a new power button. If taking out the dent and or a new power button flex cable does not work, then you may be out of luck and may want to try reaching out to Razer as you should still have a manufactures warranty.
Hope this helps!