Wacom Cintiq Pro 16 problem?

I am brand new to Roll20, and am only using the free account. I have a Wacom Cintiq Pro 16 tablet interface and I was hoping to be able to use it to quickly draw out maps on the fly for the campaign I am just starting. Problem, when I select the paintbrush and attempt to use any of the options within the menu (freehand or line or anything else) the only thing I get on the grid is a dot, and that is only if I tap the pen to the screen, if I try to actually draw anything, nothing happens. I have used my mouse and it works fine. Left click, draw, release, a line appears (again, whether using line or freehand options). I have attempted to turn off the snap to grid options to see if that was the problem (they were off and I turned them on, tried, turned them off, tried again, same results). I even tried setting the button on the side of the pen to Left click as well to see if maybe I could work around. Nope. Still not working. Even tried keeping the pen a certain distance from the screen (so the mouse icon is still visible, if anyone has used a Wacom tablet like this, you know what I mean). Still nothing. I know it is not the tablet or pen itself, because it works in every other art program or other utility I try to use it in. What am I doing wrong? Please help?

The Roll20 app is made for tablet use, but if you are accessing Roll20 only trough the tablet's browser, I have the understanding that Roll20 doesn't explicitly support/optimize for touch experience. IIRC the app is a paid freature. If you search the forum for post related to tablet  usage, you might find tips on how to improve your experience.

Just so everyone is on the same page, the Cintiq is an peripheral, not a standalone device. It is a display that supports touch, but runs the system software and browser. While Roll20 may not support some touch features, this is not quite the same as running on a tablet, and certainly not like running a tablet app. Casually Challenged, You might need to fiddle with your Cintiq settings, including Permissions and Accessibility control panels (if you are on the Mac). I can use the freehand tool and pen on a Wacom Intuos, which should work the same (minus the sweet, sweet display).

Correct, this is not the app, this is Roll20 browser. I am using Chrome and am on PC. I will look into some settings to see if those might be the issues.

Try disabling Windows Ink in your Cintiq properties.  It tends to cause issues with all tablets and drawing displays with Roll20. I has with both my drawing tablets and my drawing displays in the past.