Thank you for posting your question to the Microsoft Q&A forum.
I have investigated and determined that there is currently a service issue affecting the Assignments app in Microsoft Teams for some Education (EDU) customers in Europe. This error can cause assignments to get stuck in loading status or not opening as expected.
After a period of time, our development team has implemented a fix, and the service has returned to normal operation. Please allow up to 24 hours for the deployment to fully propagate across all environments.
After this time, you are still unable to access your assignments in Teams, we recommend contacting your school administrator (or IT department) about the issue and ask them to contact Microsoft technical support through the Microsoft 365 Admin Center.
If you're a tenant admin, you can create a ticket through the Microsoft 365 Admin Center. Once you've created a ticket, a live agent will contact you directly and help with an in-depth tenant investigation. They'll prioritize investigating your tenant and help you resolve the issue as soon as possible.
If you need any further assistance or have any further questions, please feel free to contact us. I will be happy to help.
Wishing you a great day ahead.
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