Could you please let us know the version of your High Sierra VM, is it a version prior to macOS 10.13.4 or post-10.13.4?
Here are some steps that I would suggest you to try:
1. Try changing the hard disk from SATA disk type to SCSI disk type, and see if the VM can boot up properly after the change
2. If step 1 does not help, try reducing the number of assigned processor cores to one, and see if the VM can boot up properly after the change
If your Mac VM can boot up after step 1 or step 2, after the VM is booted up, please use App Store to upgrade your Mac VM to the latest 10.13.6 version. After the macOS VM is upgraded to 10.13.6, the issue should no longer exist , you can then restore the VM to its previous settings, for example, changing the hard disk back to SATA disk type, or changing the VM's processor cores to its original value.
Thanks for helping out!
The guest OS is the High Sierra 10.13.6
I tried the items 1 and 2 using an already encrypted and it didn't boot stil.
I also tried it starting a new VM and then encrypting after changing SATA to SCSI and the have 1 processor. Still didn't work.
More suggestions are welcome!