MyrTheMoth

My Warframe and Microsoft accounts are different emails, so doubt this is the case, it's probably something to do with how the warframe website is handling the tokens provided by Microsoft after permissions are given.

Did you change the language of the Warframe Website or the language of your Microsoft/Xbox account?

Nope, same issue, seems not to be browser related, I also went to microsoft.com/consent and revoked the warframe permissions to re-authenticate, nothing, I get an email that warframe successfully got authorized, but the account doesn't get linked and instead I get the same "you are already logged in" message on the main warframe homepage

This was happening yesterday too (I was in the prime access wave), tried it again today hoping it may sort itself out, but I'm thinking it may be something extra.

I've been trying on both Firefox and Chrome, but every time I try to link my Xbox account to my PC account, it kicks me to the homepage of warframe.com and tells me "You are already logged in" in a toast popup notification at the top of the page. I disabled adblockers and any other cookie/tracker modifier plugins on both browsers, but nothing, I managed to link my Nintendo and Sony accounts just fine though. EDIT: This was happening yesterday too, before it was open to everyone, I was in the Prime Access wave.