How To Port Forward Your Xbox One & Open NAT (2019 still working!)
How To Fix Double-NAT (Two Routers) | PLEX Media Server
Using two routers, one from the internet provider and one for WiFi, causes a double-nat situation, so you can't remotely access your media. Just need to do some port forwarding and you should be able to access your media anywhere. Come for the info, stay for the arbitrary censoring.