Like the title says, I can't watch Oxygen. I've tried unlinking TV provider and relinking. Uninstalled the app and reinstalled. I'm so frustrated!;
After removing a channel, best practice is to clear the Roku's memory by restarting it before reinstalling the channel. Without the restart you may not get a clean reinstall.
So the process is:
You'll find the System restart option under Settings > System > Power on some models, or if not there under Settings > System ... or just unplug from its power source for a few seconds then plug back in.
(Note: if you have a Roku TV with "Fast start" enabled, turning the tv off and back on just puts the TV into and out of a standby state and does NOT give you a complete restart - use the instructions above.)