When clicking "Sync Back" during failback process you would see below message :
VLCR version 7.27.4.1
VLCR does not support failback or sync back for a VM that underwent sVMotion from vSAN back to SCFS in the rSDDC.
Doc for reference : https://techdocs.broadcom.com/us/en/vmware-cis/live-recovery/live-cyber-recovery/saas/using-vmware-live-cyber-recovery/running-a-recovery-plan-for-failback/sync-back.html
As a workaround customer can perform the below steps :