Channel must include language localization associated with region in order to be added to devices in the region.
If language associated with region not selected in Developer Dashboard, end-user experiences error at attempt to add channel to his/her Roku account within region: 'The channel code provided is associated with a channel not available in your region.'
Fix / Answer
Add languages associated with all regions included in channel:
1. Manage My Channels > your channel > Preview & Update > Preview & Publish (dropdown menu) > Properties > click all regions and associated languages your channel requires (see image below) > Save
2. Navigate to Preview & Publish (dropdown menu) > Channel Store Info > add Descriptions for each language listed (see image below) > Save