Chosen Solution
In the process of replacing the battery, I accidentally tore the cable of the taptic engine. I got a new part and installed it, but all the other functions are working, only the vibration is not working. I also bought a new charging dock and replaced it. There is nothing wrong with the home button. Charging, phone, camera, speaker, etc. all work normally. However, even if I purchase and install a new taptic engine, it is still not vibrating. Why not only vibrate? I’m looking for a way. 업데이트 (2021년 01월 08일) After several months, a new phase has come. In the process of reassembling the Taptic engine, I tried working with the power on, and surprisingly, the vibration of the home button came to life. However, other vibrations sound only once very briefly and not again. Still, vibration survived when switching ringtone/silent, and various vibration functions were activated. The only problem is that when I reboot the iPhone, all vibration functions disappear completely again. Whenever that happens, just remove the taptic connector after disassembling it with the power turned on, and then the vibration will survive. At the moment, I think it is the best measure, so I am satisfied and in use. However, the cause is still unknown.
One thing you could try to rule out a software issue, would be setting it back to factory settings. As there’s no problem with other functionalities, there could be a contact problem where the tapic engine and the contact points on the flex.
