When you link your gamertag to a different account, all your content and progress is lost. You'll need to link it back to the old account to get everything back, but you'll have to wait 6 months to be able to do that again.
If you changed the linked accounts, your content and progress will be lost. To get it back, you'll need to relink the original accounts. However, accounts can't be linked again for 6 months. More information on this can be found here.
@EA_Aljo playstation. and then i bought an xbox played on xbox forgot. had an old apex account so i linked my xbox account to my old platform so i can get all my stuff. but that obviously ain’t work because now i don’t have anything