Sorry for the confusion. You should've received an email/notification with details on why your channel was demonetized and the steps to resolve it. More info on this topic here: https://yt.be/help/d8W5 . Hope this clarifies!
I haven't receive any emails about my channel being demonetized, all of my contents were fine before I set my channel to private. It's just after I set it to private and then back to public days later, I lost my monetization feature. Please help.pic.twitter.com/w2zpaul6MP