What is meta?
- Any Stack Exchange user can ask a question
- The community provides support, votes on ideas, and reports bugs
- Your voice helps shape the way Stack Exchange operates
The account on Mathematics is unregistered, and it cannot be linked to other registered accounts you have on other Stack Exchange sites.
You need to register an account on Mathematics, using the same OpenID account you already used on Stack Overflow.
The accounts on Stack Overflow, and Meta Stack Overflow are already linked together.