Joe of Loath wrote:
First off, take the cable out of the clamp on the derailleur. Does it move when you click the shifter?
If yes, it's the limit screws. Undo the H one and pull the derailleur away from the wheel (this works best with no chain) until it's aligned with the smallest gear. Then let go and undo the L one until it's aligned with the big gear.
If the cable doesn't move, it may be snapped, rusty or the shifter is broken. Report back if this is the case.
I will go and check the bike now, but this applies to both front & rear shifters, they have both been stuck or fixed in place so that the gears dont change. I will pop down now and take the cable out of the clamp and then look for movement in the cable? presumably. will report back shortly.