In my case I am simply using the 'Basic Preflight' profile which came with the 'Easy Starts'.
I am experiencing the same issue today as well. this is true on a new install with simply the lastest version of the Easy Starts loaded.
No good ones... You could try exporting all the hot folders / workflows / etc. and uninstalling / reinstalling. Beyond that this is something that should go to the hotline as it requires development involvement.
All my preflights are erroring.
I get the same message:
"failed to initialise preflight engine PTB_eerrUnkown"