To enable ads on your device, you can solve that in the following way:
Open chrome browser -> pressing setting button (the 3 dots) -> press settings -> press site settings -> check that this setting is on "ADS" on "Allowed".
If the setting is showing "ADS" on "blocked on some sites" it won't work. It really needs to show only "ADS" on "Allowed" to work.
If it makes it easier, you can also see it in a movie here:
https://www.youtube.com/watch?v=qjVNo_a_4vI
Also make sure that wifi is on when you boot up the game.
Playing with wifi on also helps to make sure your game progress gets saved in the google save.