Recently I started experiencing problems receiving notifications within Teams. I spent some time fiddling with the settings and checking my Windows notifications to make sure nothing was being blocked. I couldn’t find a solution so reluctantly left things not working correctly.
On the 26th February, Microsoft announced in the M365 message center that some users have been experiencing issues with notifications. In the message Microsoft stated they are currently working to repair the ‘All activity’ option for teams and channel notification settings.
If you are experiencing these issues and would like a work around now before waiting for Microsoft to rectify the issue you can do by changing the channel notifications to custom.