VMware Workstation 16.2.4 on Linux.
Trying to convert a monolithic flat disk 500GB into a split disk.
command used:
vmware-vdiskmanager -r "/home/user/flat-disk.vmdk" -t 1 "/home/user/newdisk.vmdk"
Output:
Creating disk newdisk.vmdk
Failed to convert disk: The specified file is not a virtual disk (0x3ebf).