StanProgress.html error: "The address wasn’t understood"

I am a beginner just experimenting with Stan. I’ve got all running nicely with my model. I noticed that while a simulation runs, Stan opens a tab in my browser (Waterfox). I interpret that that should tell about the progress in simulations, which I would pretty much need. However, that does not seem to be working as the the opened tab returns only an error message. What should I try to do?

I am running Rstan 2.17 in R 3.4.4 via Emacs ESS and I use Windows 7. In the function stan(), I apply 3 cores and besides that only the defaults.



You may want to call stan or sampling with open_progress = FALSE.

Thanks! That solved it.