connect to mi band 4-5-6

[advancedcodingenterprise]

I see it in many newer BLE devices they require confirmation by the device itself for the connection. Which means I have to invoke some sort of write function (I guess) so I can establish connection.
The example I can give and I have troubles is with Mi Smart Band 4.
I am bonding the devices - connecting then when I try to subscribe for heartrate or read hearrate data (on appropriate characteristics) I just don't receive anything. I was wondering if the device required PIN or if I am missing anything since all connections are successfull except reading the data.
Then I saw that the native app of the band forces somehow the band to pop a confirmation for the connection. Now can anyone give me a clue how this can happen? May be I have to write on some characteristics?

[graphefruit]

So after you can establish the connection but don't receive any data:
What happens when you write some kind of empty bytes to the device after connection?

I know this from my bluetooth devices, where some devices needs a "starting" signal to send the data then after connection.
But I think you need to find out which exact command you need to write.