I had the same problem, and it sounds like the same one you are having. From Lightroom, I would select the Edit In-Topaz Studio and then edit copy with adjustments, and Lightroom would create the tiff file but just set there. The following is a reply I got from Joe:
I am sorry you are having trouble with your Topaz Labs software!
This problem is due to a broken Lightroom External Editor Preset, which you can fix with the guidance in the Accessing Topaz Labs in Lightroom article. Basically, you need to update the Topaz Studio preset to point to the Topaz Studio.exe file, wherever it is installed. Once you update that preset, you'll be able to launch Studio as an external editor.
There was a link in the original response, but don't know if that copied. Hope that helps.