Strange. Only things that come to mind are is your video host still active? Could your credit card have expired and maybe your Vimeo/AWS account shut down, therefore no videos ever play in Roku and they shut it down for QA?
Otherwise there was a change on April 1 of this year for channels running ads, needed to create and include an app.ads.txt file or something. That or the blackout last Thanksgiving timeframe, maybe search your email for Roku from around then for what was being impacted and changed. If you need help with the ads.txt let me know, although you would need the channel re-setup at that point.