Unity Ads fail to run after exiting game and returning

Hello!

I am running into a strange problem. I have rewarded video ads running without any difficulties, however when I exit the game (with a button utilizing application.quit()) and get back into it, rewarded video ads do not load - it simply rewards the player without any ad. I have ensured I have the ShowResults set, however this only occurs when I utilize the application.quit() function. If I simply exit the app by clicking the home button on my phone, and get back in, this doesn't occur.

So am I missing something when exiting? Do I need to clear the ads cache or something upon exiting?

Thanks for the help!