Dear @Mary Surawski,
Welcome to the Q&A Community.
We appreciate you taking the time to share a detailed explanation of the issue. Based on your description, I'd like to offer the following insights and recommendations to help address the issue.
You can attach up to 10 resources per assignment. Maximum file size per resource is 500MB
Supported attachment methods include Device, OneDrive, Class Notebook, Link, and apps like Flip or Wakelet.
For reference, you may check this link: Attachments for an assignment in Microsoft Teams for Education - Microsoft Support
You can refer to the workarounds listed below:
1.Try a Different Network
Switch to another network and disable VPN if active.
2.Upload via OneDrive
Upload the file to OneDrive first, then attach it from there in the assignment.
3.Check OneDrive Permissions
Ensure OneDrive is accessible and not restricted by your organization.
4.Clear Teams Cache (Desktop)
Quit Teams
Go to %appdata%\Microsoft\Teams and delete contents
Restart Teams
For reference, please check this link: Clear the Teams client cache - Microsoft Teams | Microsoft Learn
5.Check Site Status
Make sure the OneDrive site isn’t locked or set to read-only.
6.Upload as ZIP
Compress files into a ZIP archive and upload it. Recipients can download and extract it.
7.Check SharePoint Permissions
Confirm that students have permission to upload files in SharePoint.
For reference, please check this link: Customize SharePoint site permissions - SharePoint in Microsoft 365 | Microsoft Learn
8.Update Teams & Browser
Ensure both the Teams app and your browser are up to date. Then try using an InPrivate/Incognito window.
You can try these workarounds and update us. If the issue still appears please feel free to let us know and we will keep assisting you. Please know that we truly appreciate your patience and understanding as we strive to support you. We are here to help. Thank you very much for your understanding and cooperation.
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