If you purchased the content on someone else's account, it is not going to show up on your account, since your account doesn't own it. The Black Emporium is free, so everyone has it. If you get in contact with EA support (big orange 'contact us' button at the bottom of this page), they might be able to help you (you will probably have to wait a while, the estimated time for live chat is always wrong, apparently. Plus it's the weekend). Otherwise, I guess you'll have to play on the account you used to purchase the DLC.
Good luck. 🙂
If PS4 works differently than PC and allows DLC to be shared between accounts, feel free to correct me, anybody.
It is different on PS4, any other DLC or purchase I have made on any of my accounts that have my PS4 as the primary PS4 shows up on all accounts. For example I bought Dying Light for myself to play, but it was playable by everyone who used my PS4
