I'm not sure those samples are meant to print on. On our XR, we can cheat and block the sensor in back so the printer thinks there is more media, but I haven't found a way to do that with our Epson. You can try turning the media thing off - sorry, I'll figure out what it's called...
Edit: the "media thing" I'm referring to is... click on the little roll icon under the power button, then go down to "Media Remaining", click into there, click on "Length" and turn it "off". That might work