How to Upgrade Veeam Backup for Microsoft Office 365 to V4c Day 0 Update
Veeam released Veeam Backup for Microsoft Office 365 on June 4, but the GA build of Veeam Backup for Microsoft Office 365 version 4c (build 4.0.1.519) was recalled due to a backup sync issue identified by Veeam quality assurance.
If you are running build 4.0.1.519 please refer to the KB3194 and install the corresponding patch.