Can't get PDFg to start

We're banging our heads on an issue - starting PDFg to use cfhtmltopdf - and I thought i'd post it here to see if anyone has had anything similar happen. 

We're on CF2016 Standard (upgraded from CF11) on Windows 2012. 

When the upgrade was done, about a year ago, we can see in the logs that the PDFg service was initially registered and working. 

But, soon after, we started seeing this error message in the logs - "Error in setting up authentication for PDFg services". 

We have done a lot of experimentation including observing the port activity in the background, and it just seems like CF is not really trying to enable and/or verify this service (perhaps because of an authentication issue).

Anyone have any similar problems?  Any ideas what it might be?

Nick