I have a Playstation account on my cross save that isnt authenticated it was my account but lost the email and password to get into it
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You will need to work with PSN support to regain access to the account. All accounts must be authenticated by the player in order to alter their cross-save setup (activating/deactivating), Bungie will not get involved and forcibly activate or deactivate it, nor will they unlink the account. If you cannot authenticate the account after working with PSN support then you will not be able to activate cross-save.