Chrome Version: <Google Chrome 59.0.3071.134>
Chrome OS Version: <Platform 9460.73.0-17.0713>
Chrome OS Platform: <nyan_blaze  (HP Chromebook 14 G3)>
Network info: <Localhost>

Debugging features (SSH server in particular) are not persisted across Chrome OS updates.
 
Steps To Reproduce:

(1) Recover the Chrome OS device with USB to a previous version (in this particular case v54 for Nyan Blaze)
(2) Enable debugging features as described here: https://support.google.com/chromebook/answer/6204310?hl=en. Briefly this requires click on the link 'Enable debugging features' on the first screen after factory wipe (the factory wipe procedure is described here: https://support.google.com/chrome/a/answer/1360642?hl=en) and ensure SSH connection to the device (try the command 'ssh root@localhost' form root console on the same device to bypass any network port blocks. This should prompt for saving the machine fingerprint) is successful
(3) Update the device to the current stable and re-attempt the SSH connection

Expected Result:

SSH connection is initiated

Actual Result:

SSH connection attempt fails with 'connection refused' even when the SSH connection attempt is run form the same device with the command 'ssh root@localhost' 

How frequently does this problem reproduce? 

Always

What is the impact to the user, and is there a workaround? If so, what is
it?

This defeats the purpose of having an SSH server for troubleshooting issues where the graphical shell fails after update. Possible workaround (for enterprise managed devices only) will be to 
-- put the device in 'Single App Kiosk' mode (https://support.google.com/chrome/a/answer/1375678?hl=en#kiosk)  
-- enable 'health monitoring features' features (also described in the article above)
-- pull the device logs from the enterprise management admin console 

Please provide any additional information below. Attach a screen shot or
log if possible.

The above workaround is both limited in scope and capability 

For graphics-related bugs, please copy/paste the contents of the about:gpu
page at the end of this report.