Hi @Deepanshu ,
One possible reason for this error could be that the databases were not upgraded to the required version before attempting to upgrade to SharePoint 2013. According to the Microsoft documentation, all databases must be upgraded to version 15.0.4420.1017 or higher before upgrading to SharePoint 2013.
Another possible reason could be that the upgrade process was not performed correctly. It is recommended to follow the steps outlined in the Microsoft documentation to ensure a successful upgrade process.
I suggest reviewing the documentation and ensuring that all the prerequisites are met before attempting the upgrade process again.
For your reference:
https://learn.microsoft.com/en-us/sharepoint/upgrade-and-update/upgrade-databases-2013
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