[2023] DLC missing [PS4]

I'm guessing this is about Surviving Mars, so over there we go.  

If you had them on this machine before it's hard to see why you would not now. Did you remove the game then reinstall it, or it's been there all along?

Do they show in your PSN account online?  

Are you 100% sure you had this content in the game before? Note that the game does not tell you explicitly what DLCs are in use or not -- the ads in the main game menu can show items you do already have, for instance.

Do they show in your PSN account online? If so do they have a DOWNLOAD button there?  

If these items were definitely in this PSN account and available to you in it at one time, I can only assume PSN have withdrawn them for some reason. I know nothing about their policies in that regard; Steam only do that in the case of a payment dispute so far as I know.

The alternative could be you did buy and have them, but in a different PSN account, is that possible?  

I was just trying to cover all possibilities, I have seen such situations before where people redeem items into one Steam account and can't understand why they are not in their other Steam account, having forgotten about the first one.

As I say if these items were in this PSN account, only PSN could have withdrawn them. We have not the power, access or ability to do that.  

Certainly if this happened to all players there would clearly be some endemic issue we'd need to take up with Sony, yes.

Given this is just you (so far as we know anyway), your approach of contacting PSN support is the right one I believe. Good luck with that!