browseURL Doesn't work on server-deployed application

Hi,
I've got a shiny application that at some point opens a URL in a new browser window with the command:

browseURL(urlString, browser = "/usr/bin/google-chrome-stable")

This runs perfectly when I run it interactively, on linux and in windows (without the browser string in windows)

However, when I try to run the application with Shiny Server I get no browser window opening, and if check my logs I see the error:

ERROR:browser_main_loop.cc(272)] Gtk: cannot open display:

The same ubuntu 16.04 machine that it runs perfectly on interactively also hosts the server where it doesn't run.

Any ideas what to do about this?
Thanks,
Andrew