The file specified is not a virtual disk

This issue occurs when the .vmdk descriptor file is corrupt or missing.
To resolve this issue, create a new .vmdk descriptor file for this disk and then unregister and re-register the virtual machine. This ensures that the vSphere Client detects the correct disk size and the virtual machine powers on properly.
For more information on creating a new descriptor file, see Recreating a missing virtual disk (VMDK) header/descriptor file (1002511).