This sounds like an ad loading issue and we would love to report this experience to our ads team.
If you see an ad that is blank or black, but contains text at the top or bottom pointing to the advertiser or company - please send us a screenshot of this experience and report it here.
For steps on taking a screenshot - refer to this article: How do I take a screenshot?
Reporting the ad with a screenshot will help our team resolve an ad issue quickly.
*9/17/20: This issue has been resolved. Please relaunch your game to see the resolution. If you're still having issues, report it here.