Run regedit and go to HKLM\BCD00000000\Objects\{9dea862c-5cdd-4e70-acc1-f32b344d4795}\Elements\24000001 if the key isn't exist - create it.
Then look at value names 'Element' with type REG_MULTI_SZ - it should be the GUID where \Windows\system32\winload.exe is placed in Elements\12000002\Element for example {f28830ea-dd15-11db-a2fc-945e49de9c61}
If it not exist - create it but ensure the correct GUID!
Then try the conversion again.
If you can mount vmdk from your VM, you can do these manipulations of registry directly in VM and then do reconfig of VM...
HTH