Solved Join app lose Notifications rights

Hello,
After some time (after night?!) My phone doesn't send notifications to other devices.
I noticed that the APP lose notification rights : (warning message on the top right of the app screen)
when I click on the message I'm redirect to the settings : join have the right to access notifications!
If I remove the right and put it again sometime it works. If not I have to restart my phone...
I have MI9T phone, join have no restriction. I get this issue since Android 10 update.
Do you know this issue?
What can I do to fix that?
thx for your help.
Xavier