There are scenarios where the upgrade might fail(Soon after initiated) due to the backup that failed.
This can be confirmed by glancing through the logs in the file updatemanager0.log under \ManageEngine\ServiceDeskPlus-MSP\server\default\log as you will find the below error message.
[com.adventnet.servicedesk.updatemgr.util.SDPreProcessorUtil] [SEVERE] : Exception occured when taking backup….. not going to proceed with upgrade
In order to resolve this, it is required to add an entry in the UpdateManager.bat file so that you can skip the backup and proceed with the upgrade. It is recommended to make changes with support team’s confirmation so please contact us at firstname.lastname@example.org with the build number and other details.
Note: Always please Ensure you have a valid backup before you initiate the upgrade