Thanks for letting us know about the issue that you are experiencing.
When logging into the Sling app make sure that you're using your email address linked to that account to sign in. If that isn't working, it's possible there may be an issue within the channel itself that the service provider will need to investigate.
Try removing the Sling channel from the Roku home screen by navigating to the channel tile, pressing the * key on your remote and choosing 'Remove channel'. Then restart your device from Settings>System>System restart. Once your player starts up again, add the Sling channel back once more. Does this clear up the issue you are seeing?
If you're still experiencing an issue, try checking for any system updates in Settings>System>System update>Check now. If the issue remains unresolved, I'd recommend reaching out to Sling directly to report the issue and request additional support. Many channels on the Roku platform is developed and maintained by the channel provider directly, and they'll be able to best assist.
Please keep us posted.
Roku Forum Moderator