@RebeccaColeman-
It's not readily apparent to most that each channel provider creates, provides to Roku, and maintains the specific Roku-compatible version of their app that runs on the Roku system. Roku just provides the platform on which it runs. If you want to view Soundcloud on your Roku, you need to convince them to create a Roku-compatible channel app and make it available.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X
