I've been getting this behavior this morning as well on my phone. I ran one ad fine on an emulator but since switching to my phone the ads run and then I click the X at the end and usually that takes me back to the game right away but instead I get another blank screen that I have to use my phone's back button to close and then I get stuck at Hailing Starfleet. I'm not sure if the rewards were actually credited or not but I'm able to run an ad again right away (after restarting since the game freezes) so I"m guessing the rewards are NOT credited.
Same here (iPhone 8, iOS 12.1.4) while running a reward doubler on a cadet mission. The ad ran fine but the Hailing Starfleet box hung up for about a minute before I gave up. Restarting showed that the client didn’t register the ad being played, so I was allowed to run an ad-doubler right away and it happened again.
Comments
I tested in my end and while I did have "Hailing Starfleet" for a bit, I did get the rewards.