Changed to T-Mobile wireless today. Now, neither TV with Roku Express will load the Sling App. It reports "network error", yet there is plenty of bandwidth available. Everything else works fine, all apps and devices.. I've hard restarted, removed app / updated Roku / reinstalled app, and been on the phone with Sling. I was told I needed to go into the sling app on Roku device, logout, and log back in...but since I can't get the app to load, I can't do that. Any ideas?
The only other player in this game is T-Mobile. Have you asked them to investigate whether they are blocking access to Sling's servers?
p.s. If T-Mobile is like most companies these days, don't be surprised if the front line support script readers don't understand what you are asking them. If you sense this is happening insist on getting passed to a higher level of support.