I've also run into a bug on both Delta.com and the mobile app. When I try to pull up my SkyMiles account activity, I get 0 results and "We're sorry. We are unable to process your request. Please try again later." I spoke with tech support and they have no reports of others with the same problems and she was able to see my recent flights. I tried two different computers, three different browsers, and the FlyDelta app on Android. This has been going on since at least Saturday. They at least now have a report of it in their system but no recommended fix on my end.