Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
What channel code are you trying to enter? That error message is what you get when you try to enter the code for an uncertified channel, i.e. a "private" channel, when the code is unrecognized. It is literally correct in that an unrecognized code isn't for an available channel in ANY region, but the message is not very helpful.
When NBC finally submitted a working app to Roku for its Peacock channel, for a short period of time people could enter PEACOCK to get it installed on their Rokus. But once Roku got Peacock added to its normal channel store the PEACOCK private code no longer worked.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T