The fact it's only PS4 that's effected does sound like it might be more of a Sony issue. It seems like people were told of the issue, but only Microsoft got on top of it.Please see this link.
Originally, there should be seven more DLCs and a summary of them.
This situation has been going on since November 20, 2018, when the DLC called "Dr. Wu's Secret" was supposed to be delivered.
It's only been a week since I started playing, but it should be an endless pain for those who have been playing since its release.
It's not a Nintendo Switch, it's not an Xbox, it's Steam, it's not Microsoft.
I want to play this game deeper on "PS4"!
I'm not confident anything will be done in the near future, due to the peak of activity from the PS5, but I do hope it gets remedied.