If you have a subscription directly with Acorn, don't access Acorn from within The Roku Channel.
Install the Acorn channel app from the Streaming Channels option on the Roku home screen, then log into your Acorn account from there.
If you see this dialog:
... if your Acorn account uses a different email address than your Roku account does, click on "Use different email" instead of "Continue"
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