Your provider hands you either a playlist link or a set of login details. Each takes a different route into the app, and each fails in its own way. One guide per route.
Both routes in, by link and by file, plus the EPG field that decides whether your TV guide fills in.
Read the guide → Xtream CodesWhat a portal URL, username and password are, the seven steps to connect them, and why a missing port breaks most logins.
Read the guide →Paste an M3U link or Xtream login into the Playlist Health Check and it reports every channel as alive, dead or unverifiable. Worth doing before you decide the app is at fault.