Thank you, that seems to have been the issue. I read did with a schematic and then imported the netlist and redid the layout. The teardrop zones now finally fill in 
I opened a PR on the GitHub repo and the author of the plugin confirmed:
You’re right. The zones are not filled due to DRC rules.
In fact, the root of the problem is that your tracks and pads are not related to any net.
I suspect that you are not using schematic beforehand.Unfortunately, this teardrop plugin cannot work on pads/tracks without nets. Indeed it would be very dangerous to consider that every pad/track without name has the same net.
The best way for you to solve the problem is to make a schematic or at least a quick netlist and import it in pcbnew.Cédric