Mac Parallels Unable to Start Virtual Windows

On Sunday morning, my Windows VM blue screened. I was able to get it working again witht he following procedure:

• In Mac Recovery mode (Apple R + Power), Terminal: csrutil disable
• Relaunch OSX, shoudl be able to start Parallels virtual
• Upgrade Parallels to v13
• Check can run VM
• Back in Mac Recovery, Terminal: csrutil enable
• Relaunch OSX, Should still be able to run VM

This KB article by parallels:

http://kb.parallels.com/124294

Which suggests using csrutil disable to re-gain access to the VM. This worked for me.

Also found this one by VMWare which has a similar vein:

https://kb.vmware.com/s/article/2151780