There are various solutions you can try if you find that the QuickBooks Migration failed unexpectedly. Firstly, check and make sure that your internet connection is stable and strong, and your system meets the compatibility requirements. Moreover, you can verify the size of the data file, or update your QuickBooks application, then try to run the migration tool once again. If it still fails, then you can migrate data manually by backing up the company file and restoring it on the new computer.

https://proadvisorsolutions.com/blog/quickbooks-migration-failed-unexpectedly/