I assume that this is a bug, because Cumulus is being tracked. Even the expenses are displayed correctly, but the receipts are missing. When I ask myself: "What has changed?", the only thing that comes to mind is the "Shop & Win" campaign, which has to do with the receipts. I'm sure it will be clarified and fixed next week!
Let's push: because I still don't have a receipt in the new period, i.e. from August 1, 2017. The last purchase shown is July 27, 2017, which was August 3, 2017.
I have also just noticed that my receipts are only listed up to 5.8.17. I can only say for sure that I made a purchase on Saturday, 12.8.17, as I no longer keep the receipts since I have them in my tablet. These are normally available immediately.