I've previously had the same problem (2 months ago) and reported it to Apple Support team. It has been resolved (without taking any actions on my end). As of Jan 30th it started again. I had an ongoing active test (for 43days) and suddenly noticed that the alternate icons are not being displayed on the app-store. I'm also no longer able to see the alternate icons tab in the product page optimization page (when i'm trying to create a new test). I've contacted the support once again. I would suggest everybody contact the Apple support team. They may escalate it on a higher level of priority.