Why am I not receiving notifications for messages in a Teams channel?

Check that email notifications for the particular Team are enabled.

To do this go to the Settings within the Team and click Notifications to verify that Email is checked.
Check that Email is enabled for the particular channel in question.
To do this go to the channel, select the ellipsis (… ) beside the channel name in the upper left corner of the window, select Notifications and verify that Email is checked.
Check your device-wide settings to ensure notifications are allowed for Teams App on your device.
If your device has an app settings menu, verify that Teams App is allowed to send you notifications.
Check for any updates to your Teams App and install them if available.
The latest version of the app may contain fixes and improvements with regards to notifications.
Check that you are signed in correctly to the correct Teams account.
If you have multiple accounts, be sure the Teams App is running with the correct one.