I assume you want to factory reset it so you can link it to your own Roku account instead of the former owner's.
If you already have the Spectrum app on your Roku account it should automatically install when you link to your account. If you don't have the Spectrum app on your account already, you won't be able to add it until Spectrum and Roku come to an agreement and the Spectrum app is put back in the Roku Channel store.
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.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X
