Incorrect rating/certificate on a page

I’ve had this problem for about a year. On the page for the webseries “The Backrooms” (imdb.com/title/tt20863294), the rating has been TV-PG. This is completely incorrect. The show has uses of “f*ck” and other profanities, making it not worthy of a TV-PG rating. Not only that, but there has never been an official certification of this show. I have looked everywhere for about a year and I cannot find an official rating “TV-PG” or not. This being said, I’ve tried to correct the rating to “Not Rated” several times, with each submission being declined. It keeps saying “Invalid evidence” although there is no evidence as the show has never gotten a rating. Can somebody please help me change the “TV-PG” rating into “Not Rated”? One more thing… the first episode (imdb.com/title/tt17291392) is also incorrectly marked as having ratings, although it never has gotten a certification, and therefore should be “Not Rated”. I’ve had the same problem with this episode as well.