Watch ESPN app unauthorized to view when logging in outside of the home AT&T network

When I am home (in Michigan) I can log into the watch espn app and view everything on the app. I always select the keep me signed in for 2 weeks box because when I don't, and say I'm not at my house, I go to sign in and it says I'm not authorized. But I've found when I sign in while on the home AT&T wifi it has no problems and can view everything. My problem is I am in the army and I can only use the app for essentially only 2 weeks after I last signed in while still on that home network that is now across the country. Why is that??? Why can't I sign in on my wifi here and be able to watch ESPN on the app on my iphone/chromecast?? It's been very frustrating and no one has been able to help me when I call customer service.