Plotting from CarlsonSurvey 2016 Intellicad8.1. (plot dialog box looks same as Acad and older versions of CS)
Dialog indicates Print Style Table (filename=1a.ctb) is missing. the browse button is ghosted, so no can browse to the file location.
(screenshot below)
Run thru the import new Print Style routine but at the end of those steps plot dialog still points to the not-missing 1a.ctb (missing) file.
the file exists, I can Windows browse to it, but not plot-dialog browse to it.
Cad gurus, please speak.
I'd send an email to carlson support. Just had a similar problem with same setup and they were extremely fast and helpful. Their support is awsome.
I don't use Intellicad or Carlson, but the concept should be the same as Autocad. Open your options or preferences (whichever Intellicad calls it), and you should have a Files tab. Within that tab, you should have a line that reads Plot Styles or Plot Style Tables. Expand that line, and you should see a default path to some location on your C drive. Browse to the folder location where your plot style table is located and set that. That should do the trick, but sometimes you may find that you have to exit the drawing and open it up again before it recognizes the new folder location.
Hope that helps.
I assume this worked before and has spontaneously quit. If you haven't rebooted I'd sure try that.
FWIW, the idea of setting lineweights and transparencies by layer and dispensing with the ctb file altogether is growing on me.
Blitz has the route I was looking for.
Found Settings>Options.Paths/Files tab>support paths and a Color Book tree. Create a new path where the Print Style Tables reside.
Reopen Plot routine to no change from before. Only plots color (the 'None' Print style)
The path in the Print Style Manager no longer exists (TOSHIBA DRIVE-ENTIRE DRIVE...). Yeah, I did a hard drive cleanup and spiked old laptop backup. But why would Intellicad use that path anyway? Never installed C2016 on laptop machine. 
the task is to change the directory from TOSHIBA DRIVE-ENTIRE DRIVE... to a path on my current desktop.
None of the Intellicad dialogs I've explored so far take me there.
Solution fr. tech support:
the color tables MUST reside in dedicated carlson support folder
c:/USer/>name>/app data/roaming/carlsonsoftware/...
Wow. This would be an example of why I dislike Carlson so much. What if you work at a company where you are keeping all your support files on a server, as you should?
The last time I talked to Lon I told him whatever problem I was experiencing was the dumbest thing I had ever encountered, but this would rank pretty high on the list.
I copy the files directly into the Carlson Support directory, and have never had a problem. It makes it fairly simple to keep things standard, if you have CAD standards. It's just part of setting up the program to work the way you want it to.
The advantages of Carlson far outweigh the negatives, in my opinion. I have found very few negatives in my 9 years of using the program.