My Xbox account is shown as linked, and I don't play on PS4 or PC. The tab that says "Continue" at the bottom is un-clickable and I can't progress further. I've tried on laptop both on Chrome and Safari with on luck as of yet.
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Cross save cannot be enabled or used if you don't have more than one account linked. If the only account on your profile is an Xbox account then you can't use cross save because there would be no point.