Please confirm that you are running one of the following versions of Veeam Backup for Microsoft 365 before upgrading to 5a:
3.0 (build 126.96.36.1992)
4.0 (build 188.8.131.525)
4a (builds 184.108.40.2063, 220.127.116.110)
4b (builds 18.104.22.1686, 22.214.171.1249)
4c (builds 126.96.36.1999, 188.8.131.521, 184.108.40.2065)
You can check this under Help and Support > About in the Veeam Backup for Microsoft 365 console. To upgrade from earlier versions, please contact our Customer Support. After upgrading, your build number will change to 220.127.116.110.
Upgrade from the beta version of Veeam Backup for Microsoft 365 5.0 is not supported.
To upgrade from Veeam Backup for Microsoft 365 builds 18.104.22.1681 and 22.214.171.1243, please apply Cumulative Patch KB4078.
If you are using Veeam Backup & Replication or Veeam Cloud Connect 9.5 Update 4, 4a, or 4b, install Veeam Backup for Microsoft 365 4a. For more information, see KB3035 and KB3089.
This form is only for KB Feedback/Suggestions, if you need help with the software open a support case