This article explains it better. First of all there are plenty of black owned media companies, more than one in Atlanta who were denied credentials:
The NNPA represents the 197-year-old Black Press of America, which counts among its more than 230 newspapers and media companies, The Atlanta Voice, Atlanta Daily World, and the Atlanta Inquirer. The popular Rolling Out magazine also counts among the Black Press’ members frozen out by CNN.
However, they were apparently all denied based on the Jun 7 deadline.
CNN implies the deadline was stated in their announcement of the debate on May 15th but the only deadline mentioned is for polls determining which candidates could participate.
President Biden and CBC and Rep. Meeks lobbied CNN for Black media inclusion after the denial.
I don’t know how these things usually work as there was no indication in any of the articles how the successfully media handled it. It seems crazy there would be such a knowledge gap.
Feels pretty obvious that seating would be limited and coveted, and there was contact information in the announcement for “more details”. If I had no idea how to get an invite, I’d have written that email May 15th. But maybe there’s more to the story than either side wants to tell.