1) Make sure you are logging in into the app using the same mobile number that is registered with Sun Direct.
2) If it still says the same as before, try using a laptop (or a web browser in your mobile) to access your Sun Next account through the Sun Next website, using the same registered mobile number and password you used for the app --> https://www.sunnxt.com/
3) After logging in, access the My Account page and verify the My Subscriptions section.
3.a) If it says you have a valid subscription, do a Clear Data for the Sun Nxt app in your mobile and try logging in again. I will probably work. (Settings --> Apps --> Sun Nxt app --> Clear Data)
3.b) If it still says that your subscription has expired, call CC and explain them the issue.
Bro, I was facing the same problem. I wrote to firstname.lastname@example.org and to my surprise, they promptly responded. In my case, two smart cards were mapped to same mobile number. One smart card is having an active subscription while the other isn't. Sun NXT app was showing no active subscription referring to inactive account. Once registered mobile number of inactive one is changed, sun nxt started to work like a charm.