Error from last API Key attempt

I keep getting this error everytime I try to activate WordPress.com Stats plugin. I’m using the same API I’ve used the first time I installed it, the domain is still the same and the API is also the same, just checked at Akismet.

Can anyone help me on this?

This is the error:

Error from last API Key attempt:

The owner of that API Key (usernameY) is not on the access list for this blog (12345678). Stats was installed using a different API key. The owner of the original key can add users to the access list, or you can contact WordPress.com support.

I’m on a self-hosted blog.