Hello costeele21,
Progress and inventory are tied to the EA account that you played on - unlinking the platform account and linking it to a new one means that it stays with the original EA account, and it's not possible to move progress from one EA account to another. This is also explained in the warning pop-ups while you unlink accounts and in this article.
If you want your progress back, you can try linking the platform account back to your old EA account - there is however no guarantee that this will work, as the original unlinking process can damage your progress.