Device Doctor: message error creating keys

I ran Device Doctor on a brand new Photon

After setting up the WiFi credentials, the Doctor responded with the message below and then stopped.

Put the device in DFU mode
Tap RESET/RST while holding MODE/SETUP until the device blinks yellow.
? Select Continue when ready Continue
Okay!  New keys in place, your device will not restart.
The Doctor didn't complete sucesfully. Make sure your device is in DFU mode (blinking yellow), and that your computer is online.: Error creating keys: Command failed: openssl genrsa -out 30001a000947363335343832_rsa_new.pem 1024
'openssl' is not recognized as an internal or external command,
operable program or batch file.

> Please visit our community forums for help with this error:
PS C:\>

So here I am visiting the community forum.
What should I do?

It appears openssl is not found on your machine.
Check if you can run OpenSSL from the command line.
Check whether you got it installed at all.
If so, check your PATH environment variable and add the path to OpenSSL to it.
If it’s already there, your path variable may be too long and you’d need to tidy it up.
Have you installed CLI via the Particle Windows Installer?
If not, do - If so, uninstall CLI and reinstall it via the installer (make sure to tick the “remove old drivers” checkbox as well)?