Additional assignment-related features and issues within Microsoft Teams for Education
Dear Skye Sings,
Thank you for posting back and sharing these detailed information with us.
We did a test from our side and cannot reproduce the situation. Once a student submits a form in assignment, the assignment will be turned in automatically.
It seems that you are using Teams desktop application, we suggest you go to Teams for the web app in browser (firstly sign in Microsoft 365 home page, click Teams icon from App Launcher) see if your assignment shows in the Completed tab. This way helps you narrow down if it's a displaying issue in Teams desktop app.
At the same time, since you have submitted the form as it shows "Your response has already been submitted", you may try to contact your teacher and confirm whether he can see you turned in the assignment on his side. If yes, it might be just a displaying issue on your side.
However, if your teacher still see your assignment's status is Not turned in, considering your classmates didn't experience this issue, it may need to check your account from back end for further investigation.
As forum support we may not have enough permission to directly check your account. In this situation, we sincerely recommend you contact your Microsoft 365 administrator, follow steps in this article and create a support ticket to contact Online Support. The support team over there has higher permission and more resource than us, they can remotely help check the situation on your side, they have the specific diagnostic tools that can help troubleshoot this issue further. This would be the most efficient way in handling this case for you.
For your reference: How do I find my Microsoft 365 admin
Thanks for your time and understanding. Hope you keep safe and healthy always!
With sincerest regards,
Tina | Microsoft Community Moderator