Can't pair without Mi Fit

Hi. I already had a Amazfit Bip Lite working with the Notify App (Without Mi Fit). Gave it to my wife and bought a new one (model a1915). I can't pair it with Notify App. The App finds the watch but on the watch remains this stupid "Connect" logo (a circle with two squares connected like a chain). And syncing doesn't work either even sometimes the app says it's connected.

Tried it with Mi Fit. Worked fine. But I don't want the Mi Fit App. I have the Notify App Pro, and I want miss the extra features.

I tried all the tipps from the tutorial. Nothing worked. There are many similar suestions in the web, but I could not find any working solutions? Any tipps?!

Without Notify App the amazfit is just trash...