I do have an android yes, but the back button is doing nothing in this particular situation. In the past if an ad wouldn't work, there was a report ad button that did work to still bypass the ad. In this case that is not showing up either. You can also see in this screen shot that there is something wrong- the "play on" ad…
I have the same problem. The issue then is that the same ad that doesn't work keeps being presented, so I repeatedly have to force close and can't get passed the flawed ad to an ad that works