ESPN3 streaming on devices but not on X1 box

I have Xfinity internet and so get free access to ESPN3. I regularly stream ESPN3 content on my laptop and cell phone. However, when I try to access the exact same ESPN3 content on my TV via my X1 cable box, it tells me that I need a subscription. It is true that my Xfinity cable subscription does not include ESPN, but that shouldn't matter because ESPN3 is free to me based on my Xfinity internet subscription. Any ideas? My workaround is to connect my laptop to the TV via an HDMI cable, but it would be a lot more convenient if I could just pull ESPN3 up directly on the TV via X1.

Thanks!