I have such an error, when I try to log into Activision via xbox, they ask me for a link to...

I only had an xbox linked to Activision, but my Activision was hacked, and now to restore Activision I need to log in via xbox, but my Xbox was blocked

I resolved the situation.

You need to unlink xbox account from activision.

1 - Go to https://s.activision.com/activision/profile

2 - Unlink the Xbox account.

3 - Access the warzone on the console and log in with the activision account.

4 - You will be asked to perform the link.

5 - I link the two accounts.

6 - Problem solved.

When I log in to Elite is has both my PSN ID and my Xbox Gamertag connected. I haven't played the game on PS3 so I can't check but it looks like one account should be enough. I do sometimes get errors on the Elite app saying I need to link my gamertag or
asking me to upgrade, so maybe it's still just a it glitchy?

Either way, I think you're better off asking Activision on the official callofduty.com support page or forum.

This seems to have worked for me, had to scroll all the way to the bottom of that list though to find activision, but it asked me to re-link my account when i tried signing in again.

It asked to relink before getting to that in-game menu where it asks for an account? Or was it no allowing you to create a new activision account when the menu pops up? My lil bro told me it pretty much forced my activision account when he signed. I would
try it on my xbox but its my account. Ive been busy with work to try it on the psn account. But if you do happen to get in with a separate account let me know! Thanks for the updated also! Its a step towards something at least.

ACTIVISION EMPLOYEES PLEASE PAY ATTENTION!

This seems to have worked for me, had to scroll all the way to the bottom of that list though to find activision, but it asked me to re-link my account when i tried signing in again.