Examine the client dsmerror.log file to see if a log entry indicates why the vMotion task failed. Additional information about the failure might also be available in the vCenter server, on the Task and Events tab for the ESXi host that you were migrating the VM from. If possible, use the log and event records to determine what caused the vMotion task to fail and fix it. Then clean up the virtual machine (use the Restore VM command with the -VMRESToretype=VMCLeanup option) and restart the vMotion task. If you cannot restart the task, suspend the virtual machine and use the vSphere web client to start the VM migration from one host to another.