The teacher says they did not receive an assignment but I turned it in.
Check to see that student is logged into their school Google Account and not another email account such as a sibling or parent. It's also important to make sure the device is connected to the WiFi.
If the assignment was assigned in Google Classroom a copy can be found in the Google Drive. Go to Google Drive and search for the title of the document.
My child is being overwhelmed with emails and notifications, how do I limit that?
This video can show you how to manage notifications. https://www.youtube.com/watch?v=xx3OqYBqHss