I also had the same issue here. I followed the above guide but it didn’t work.
- Setting
Virtualbox 5.2.18
macOS High Sierra version 10.13.6
Docker version 18.06.1-ce, build e68fc7a
When I ran the step 3 command alias local-docker-machine="/Applications/Local\ by\ Flywheel.app/Contents/Resources/extraResources/virtual-machine/vendor/docker/osx/docker-machine"
nothing is changed,
Then ran the step 4 command it was not working (“No such file or directory”) So I replace the command “local-docker” to just “docker” following the other’s approach.

But even after this,

the “Regenerating Docker Machine Certificates …” message is repetitively shown.
Sometimes I can see the screen “Looks like you haven’t create …” some normal screen but it only lasts for one or two seconds then the Regenerating Docker Machine Certificates …" message and the “Checking System” is shown so I can not do any works here.
Should I reinstall the Local by Flywheel? At first when I installed this program I also had the issue for the 2nd bar part (I can not remember what it was exactly)

After this “There was an error validating certificates for host” error, I just kept going but it was never ended for the 2nd bar part.
So I googled and the answer was just turning off the local by flywheel in the virtualbox and restart the local by flywheel. So I did then the issue for the “Regenerating Machine Certificates” is newly detected.
Please help me !!! 
Much appreciated,