Sorry to hear that you're having this experience.
Thanks for letting us know all that you've done. If removing the channel and adding it back after you've restarted the device does not resolve the channel issue, I'd recommend reaching out to the channel support directly to report the issue and request additional support. Many channels on the Roku platform are developed and maintained by the channel provider directly, and they'll be able to best assist. If other channels are working correctly, and you only experience this issue on that channel (app), that is likely an indication that the issue lies within that particular channel. In these cases, the channel provider will need to investigate the issue in order to help resolve it.
You can reach them here: Help Center (tubitv.com)