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"The remote server returned an error: (403) Forbidden. Access denied" when performing Veeam Backup for Office 365 backup

"The remote server returned an error: (403) Forbidden. Access denied" when performing Veeam Backup for Office 365 backup

KB ID:	4156
Product:	Veeam Backup for Microsoft Office 365 \| 5.0
Published:	2021-05-07
Last Modified:	2021-05-11

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Challenge

Backup and restore operations in Veeam Backup for Microsoft 365 fail with the error:

"The remote server returned an error: (403) Forbidden. Access denied"

Impacted Configurations

Backup operations for Veeam Backup for Microsoft 365 deployments with Organizations using these authentication types:
- Basic Authentication
- Modern Authentication and Legacy Protocols
Restore operations for SharePoint, Microsoft Teams and OneDrive within Veeam Backup for Microsoft 365 deployments with Organizations using these authentication types:
- Basic Authentication
- Modern Authentication and Legacy Protocols
- Modern App-Only Authentication

Cause

Recent changes made by Microsoft to their APIs have impacted certain authentication queries that are used in versions of Veeam Backup for Microsoft 365 prior to build 5.0.1.225.

Solution

Users must upgrade to latest version with Veeam Backup for Microsoft 365 5b cumulative patch KB4135.

The newest product build leverages different API queries which help to avoid the permission issue which takes place in older builds.

If after upgrading to Veeam Backup for Microsoft 365 5b (5.0.1.225) the error still occurs please create a support case and provide a full log bundle.

More Information

Veeam Backup for Microsoft 365 5b cumulative patch KB4135
Veeam Backup for Microsoft Office User Guide - Collecting Log Files - the link.

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