This happened to me. I was denied when I tried to apply for Hilton Biz card last month.
I was only 4/24 (3/6, 4/12).
The rejection letter cited one reason: "Too many new bankcards".
When I called for recon, the agent said if I try again in July I should be able to get it.
For now, I am just working on spending bonus on my existing cards.
Sorry you didn't get the card this time.