In my case, it helped to change the units of measurement from millimeters to mil

* This may be due to a rounding problem between mm and mils. Sometimes if the PCB is originally specified in mils and the setting changed to mm, the rounding errors can make the some dimensions appear to be outside the design rule settings. Switching back to the original units usually fixes this issue. * Also check your autorouter Layers config: 

Thanks Tamul and Andy! The problem ended up being i had a ground plane over the entire board with the center masked out (so it just defined a grounded perimiter) - this caused the autorouter to fail, once i removed that and defined it instead as 4x individual rectangles, it worked fine as expected! Hollowed out planes don't play well with the autorouter, it must see it as a giant rectangle or something. Anyway it's all good - so impressed with the entire toolchain of this package, it is SO easy to go from schematic to ordering some boards. Very cool!

@SaltyBrains, Glad you're sorted and like the tools!