Please confirm that you are running one of the following versions of Veeam Backup for Microsoft Office 365 before upgrading to 5b:
You can check this under Help and Support > About in the Veeam Backup for Microsoft Office 365 console. To upgrade from earlier versions, please contact our Customer Support. After upgrading, your build number will change to 220.127.116.11.
Before you apply this update, be sure to review the ‘Upgrading Veeam Backup for Microsoft Office 365’ section of the Release Notes document.
For detailed information about this release, please refer to the Release Notes document.