WordPress.com Stats: “You are not a member of this blog”

I keep getting the following message

“If you have just installed the Automattic Stats plugin, this error probably appeared because the API key entered in the plugin belongs to a different WordPress.com user account.

* Have the owner of the API key visit this page and add you to the blog, or
* Get your API key here, then deactivate and activating the plugin and enter your key to add your account to the access list for this blog.”

I used my Akismet key as the same key, and I did go into users and add the name of my “wordpress” blog, but nothing seems to help.

I can’t figure out how to fix this.