no notifications since the last major update

Hello, everyone,
Since the last major update for K-9, I do not get push messages and no notifications on the lock screen. The settings in K-9 should fit so, under Android, notifications for K-9 are allowed. What can it be?
Android version: 10
K-9 Version: 5.806
Hardware: Xiaomi Redmi Note 7

My english is not that good, so I let this translate this by Google.
Many times
Greetings Andreas

Try 5.904, the notification issue was already fixed in 5.902.

Why can’t I get such an update from the Google Playstore?
But it still doesn’t work!

As far as I know you can once you join the Beta program - 5.9xx is Beta version of K9.