Horizon Instant Clones provisioning fails with the error: "Unable to prepare migration"

Sometimes we have face this issue while creating instant clone pool.

If you have already tried to set Esxi hosts in maintenance mode ,even set attribute instantclone.maintenance=2 but still you are facing same error.

This KB if you have already followed : https://kb.vmware.com/s/article/60397

Then try this workaround : Power off your parent template , go to edit settings => VM options => Advanced => edit configuration => remove any value against this attribute "namespaceMgr.db".

=> Power ON parent VM

=> Gracefully shutdown and take new snapshot.

=> Publish new snapshot in Instant clone pool