Amazfit Watch faces

I am a Mi 9 user, I downloaded the amazfaces app by referral on youtube and any watchface I click install, even with the paired mi band, is like "Upgrading firmware" endlessly and does not install.
I tried to follow this tutorial, but it doesn't have the folder "/Android/data/com.huami.watch.hmwatchmanager/files/watch_skin_local/", only "/Android/data/com.amazfitwatchfaces,st/files/".
Already tried to restart bluetooth, reinstall amazfaces and was unsuccessful.
Can someone help me please?
I am a user of a Mi Band 4.

Hey, I know I'm late to help you out but if you still need help you can take a look at my guide. I also couldn't install watch faces using the method you linked so I had to use some apps, namely "miband4" and "mifit" app.

installation starts at 1:46
https://www.youtube.com/watch?v=DwJXyRHkxXc

I had exactly the same problem with the mi band 5. The installer is broker. Also for the mi band 5.
Better to use the MiBand4 app available on the AppStore, as described by the previous poster. It works flawlessly.