There is a silent mode in the Tinymight that can be accidentally activated and then the vibrations would disappear. But this can be reset easily by opening the battery lid and closing it again. If this does not solve the issue, the most probable reason is that the vibration motor contacts have flattened and don't make a strong enough contact with the electronics board.
it is a very quick and easy to fix. Tools needed: Torx T20 screwdriver / bit and something like a small screwdriver.
1) open and unscrew the big back end screw with the Torx T20 driver. It is a long one, and please hold the top panel when removing the screw, as it will come off otherwise and we don't need that. After the screw has been removed, you are ready to take off the bottom aluminum end panel.
2) the USB charging connector is often a little bit stuck in its hole in back panel. if you just try to pull the panel off, the electronics board is trying to come with it, which is not good. So we recommend to use something small, like a small screwdriver to push same time the USB connector down while pulling out the panel, and all should be easy.
3) You will see the vibtarion motor in the inside of bottom panel. It is placed in its rubber boot, and the upwards facing golden contacts might need to be bent a little but upwards to get them to make a stronger contact with the electronics board. Plese note, that to install the bottom panel successfully, we recommend to hold it in such a position that the button is hanging downwards, this way it will stay where it should and the panel should slide easily on top of electronics board and you can tighten the screw again very well.