Forwarding this to be more recent that @oxTHESNIPER_PSN shared and saved me from tossing the PS5 in the lake
EVERYBODY, I just fixed it on my game. what you wanna do is go to MLB the show website, click on my account, instead of clicking on your console click on the MLB the show account option, log in with your the show login, and then once you're logged into that link your console, once you sign in to console through mlb the show account, it'll give you two options, it'll say choose your console account(which is restarted version) or your mlb the show account which will have your correct stubs and inventory. click on that one and close app on console then re open game and it should all be there. I just did this and it worked I promise.