This should be impossible. We actually have constant monitoring to ensure that zap receipts are always created for users of Rizful. That said, it is totally possible that there is a networking issue on your end, on the relays you have subscribed to, such that you don't see the receipts in your browser.....
I stopped using it for receiving zaps cause zap receipts were not being broadcasted for zaps I received. Works great for sending with NWC though. I switched back to good ol nostr:npub1hcwcj72tlyk7thtyc8nq763vwrq5p2avnyeyrrlwxrzuvdl7j3usj4h9rq for receiving.
Discussion
I’ll try it out again. I only have a few relays so maybe they just missed the receipts for a few zaps.