I managed to connect mine. I just paired it like when you first pair your device. I don't know if you need to be paired with mifit also.
I signed into zepp with my mi account, and it seemed to work fine.
Hi, I found there is another method which you doesn't need to use Mifit
1. Connected your band to your phone by "Unlock with Bluetooth device " in "Bluetooth and security" ( reset the band if you want, delete Mifit)
2. Open zepp and connected the band.
If it doesn't work, reset the band 1 more time ^^
Tested and worked with me 😀