Hi, Sync and Redeem are 2 different features. You can Sync as many times as you want. I think you got those terms mixed up, so we're not sure what's the problem here.
Please attach a screenshot so we can see it better.
About the past DLC, those are unlocked, but hidden by us, as it's not playable yet in the Remastered. We will unhide them as we update the game.