Thanks for letting us know. We've received similar reports about ads playing on channels that aren't part of YPP. We're currently looking into it. That said, mind sharing a screenshot of your channel's monetization page: https://yt.be/help/qCTR ? Keep us posted.
Thanks for the screenshot. This means our review team has not come to a clear decision during the initial review, so we’re putting extra effort and resources into reviewing your channel multiple times before making a final decision. Hope you hear back soon.