Delta American Express card holders should try this link.
There’s a targeted ‘renewal bonus’ of 7500 miles. It’s not clear who or how many personal cards are eligible. I would have expected folks who are coming up on their renewal date to be the ones targeted — get 7500 miles a couple months after your card renews — but according to Flyertalk even someone with a brand new card was eligible.
It’s a free 7500 miles if you’re able to successfully register your card.