Best Wordpress plugin to engage your users and collect their email. You can use header alerts, popups, or exit pages, and it works with any popular emailing service such as Mailchimp or AWeber
I just ran into the same thing, and the problem was there was a space after my url listed in the Change URL box of WP Subscribers site (where you list your authorized sites, not the WP area on my site).
Once I backspaced to remove that space, I was able to get authorized in WordPress. I've read whether you have a / at the end of .com/ or .com can cause the same problems. The characters have to match exactly.