Membership Problems with PayPal Payments Standard Gateway

I trying to set up a subscription for my site. $5 first month and renews every month thereafter at $10 per month. After register a user, click subscribe and am directed to Paypal payment page I log in through Paypal sandbox mode I get this error:

Sorry — your last action could not be completed
If you were making a purchase or sending money, we recommend that you check both your PayPal account and your email for a transaction confirmation after 30 minutes.

If you came to this page from another website, please return to that site (don't use your browser's Back button) and restart your activity.

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Message 3005

I have gone through old forum posts and still can't seem to get this to work. Any advice? Thanks!

http://socialharmonygroup.com/register/