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"400 - Bad request - Value cannot be null. Parameter name: token" when performing Microsoft Teams backup 


Microsoft Teams backup may fail with "400 - Bad request - Value cannot be null. Parameter name: token" error.


If a user never opened the Files tab of a team channel in Microsoft Teams, this tab is not linked to the Files document library in a corresponding SharePoint team site. In this case, Microsoft Graph request for such a document library fails with "404 - Not found" error. 

Since recently, the error code in Microsoft Graph response has changed to "400 - Bad request - Value cannot be null. Parameter name: token". Veeam Backup for Microsoft Office 365 fails to interpret this unexpected response and cannot successfully continue backup of such teams.


This issue is resolved in cumulative patch KB4124 for Veeam Backup for Microsoft Office 365 5b.
KB ID: 4123
Product: Veeam Backup for Microsoft Office 365 5.0
Published: 2021-03-05
Last Modified: 2021-03-12
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