Hey, that error can be frustrating! A few things that helped others with similar issues:
Make sure your Microsoft account isn’t already linked to another platform or console. Sometimes unlinking old devices helps.
Double-check your privacy settings on the Microsoft account—cross-play permissions sometimes get blocked there.
Try signing out of both the PS5 and Microsoft accounts completely, then sign back in fresh.
If possible, test linking on the Microsoft account website first to see if it prompts any error or verification step.
If none of that works, sometimes waiting a bit and trying again later helps too, as it could be a temporary server-side issue. Hope you get it sorted soon!