Hi Kath I am Having issues on my iPhone 5s currently the software is up to date 9.2.1 OS I have watched sky sports on my mobile previously but now every time I try to it asks me to sign in even after I already have signed in , or tells me I need to upgrade, but I already have the full sports package subscribed
When you sign into your TV Anywhere account, on the right under My Profile click on Sky Movies & Sky Sports. Does it show the iPhone in question as registered?
If so, as you have a device change available, can you remove the iPhone from the list, then go back onto the Sky Sports app on the iPhone, select a channel to stream and this will prompt for re-registration. I have also re-sync'd your account to see if that will help.