Notifications are not sent to Mi Band

Hello!

Message and mention notifications are sent to my phone correctly but they are not sent to my Mi Band (though all necessary settings for Mattermost are set in Zepp Life).

Have someone come across to this problem?

Phone: Xiaomi Redmi Note 8 Pro, MIUI 12.5.3 (Android 11)
Band: Xiaomi Mi Band 5
Mattermost:
App Version: 2.15.0 (Build 6000512)
Server Version: 9.3.0 (Build 7014621505
Database: postgres
Database Schema Version: 114

UPD: Notification are come to the band but it happens hardly ever. I can’t explain in which case this happens because it seems to be random