That, or at least measure the voltage between the hot and neutral line input terminals of the GFCI to make sure there's 120V present with the switch ON and you are trying to reset the GFCI.
If it appears the voltage is there but it still won't reset, I suggest you remove the GFCI and temporarily power it through a line cord (after taping up the terminals for safety) or install it at a known working receptacle location, so that you can verify it works properly. That's to double check in case there might be some very short voltage dropout on the switched circuit that's preventing the GFCI from resetting, maybe from a bad switch or whatever.
