Okay, so a long time ago they continued making physical collector's editions well into the expansion. At one point during Heavensward, I already owned Heavensward but I kinda wanted the physical collector's edition. I was also missing the digital collector's edition items. I saw the physical collector's edition go on sale for half off. I bought it thinking I get the physical collector's items AND the digital ones by buying this. Once is came in the mail it only had one code inside and that was both a code for activating Heavensward on the account AND for the digital items. Since I already owned Hevaensward, I couldn't use the code meaning I had to buy the digital collector's upgrade on the mog station for $20. This is probably what you're experiencing. Buying the complete edition gave you Shadowbringers and now you bought the collector's edition but cannot put the code in because you already own Shadowbringers from the complete edition. There's a upgrade to digital collector's edition button on the mogstation website for $20. This is how you should upgrade to digital collector's instead of buying the complete and collector's edition on the square enix store.