I am having the same problem. I have 3 locations that I have spectrum TV. Yesterday I cancelled one location to internet only. Now, when I go to the Spectrum app there is not an option to sign in. I think Spectrum puts a block so you have to pay for their TV package. Did anyone find a solution?
Okay. Let's try this then. Delete the channel, then unplug the Roku. Unplug router/modem, and wait 5 minutes. Power up router/modem, and wait for the internet to come back up (check with laptop/PC/Phone). After you've confirmed the internet is working, power up the Roku, and then re-add the channel.
If that still doesn't work, send me your serial number and firmware version and build number (Settings > System > About), as well as the last known time you tried to access Spectrum (date/time), so we can check the logs.