Would need more info than that but the likely reason is some vpns get blocked by tv companies when they pick up it's being used. It's usually done against a range of IP addresses so swapping to another of the connections available from the vpn company may work.
Thinking outside this specific incident, where are you, how often do you want to watch things, what is it you want to watch, is it always on your phone or would you prefer to watch on tv and are you prepared to pay for it or are you using a free vpn?