vibrate/ mute button not working

The tiniest part in the world is what apple thought would be a good design for the vibrate toggle! Take the screws back off the vibrate toggle and have a good look at the groove on inside of vibrate switch and how the tiny plastic toggle should fit into the groove. Next I'd secure the outerr vibrate switch with tape so you have both hands free to place the toggle into the groove ( helps if it is down position and so is outer switch). If this still fails to make vibrate work take a look at the vibrate motor - sometimes the prongs just need lifting up a bit to make contact with logic board