Just sharing what I learned after quite a bit of googling about the Hear Rate not measured in Mi Band 2. I bought a Mi Band 2 mid of last year and everything worked fine.
However towards end of last year the Heart rate measurement showed...
Just flashed v22 on revolver 3.5 , running fine. Voltage options are back in SetCPU.Voodoo works as well.
However the NTFS USB drive is not listed under removable drives.After plugging in, it shows a very short preparing external USB and then it ...
Found it in Buttons in settings and remapped to long press menu key.
Decent but the lack of multi color LED notification is a big downer.
Ensure that you login with phone number of Mi account and that there are no other devices in Mi account. If it still doesn't work as it did for me, post in MIUI forum and they will add you to senior group and it will work like a charm