Unity ads dont work in some phones in production google play, help!! its urgent

hello how is it, the first time I write in this forum, I'm having an annoying problem, I uploaded an application to android ios, in ios the ads work well and everything is fine, and in android however in some cell phones I'm fine and they appear, and in other cell phones they do not appear, you can not get coins for watching advertising and it does not appear in advertising when one dies in the game, the strange thing is that cell phones work well, but not in others. If you know or have an idea, you are very grateful, I have the game id id, and update unity today to the latest version. With a phone went and is connected Google Play games (to save the data) works, and if not, you can play without advertising.