Like nielsoncp, I am also using Sketchup Make 2017 on a PC. You can also grab the exporter here:
https://sketchucation.com/pluginstore?pln=OBJexporter
It requires you to sign up for the site, but you get an .rbz file which you can install from the Extension Manager inside SketchUp.
I would also
strongly recommend watching silvam14's video tutorials in the stickied thread.