My app shows past stays.

Go to the Account tab, it shows the progress screen. Up top it says ‘account’. The second option is ‘past stays’. It will show all stays and receipts. The first option is. ‘Points activity’ and it will show how many points you earned per stay.
If the stay is missing, then you know which one isn’t being counted.

PS. I have one night left for Diamond and I’ve been tracking it closely.