You can read the detail description in this issue.

The fix is, find out the listener service with this adb command:

adb shell pm dump io.github.jd1378.otphelper | grep -i "notification\|listener"

And you can see it’s called io.github.jd1378.otphelper/.NotificationListener.

So, we grant it special access to read notifications (which is not possible via settings GUI, and I don’ know why):

adb shell cmd notification allow_listener io.github.jd1378.otphelper/.NotificationListener