Why am I getting an "invalid link" error when trying to do a PayPal subscription?

I'm getting an error when I'm trying to setup payment through this paypal subscriptions form. I'm testing it using the PayPal sandbox.

I'm getting the following error:

The link you have used to enter the PayPal system is invalid. Please review the link and try again.

My code looks like this:

<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post">
    <input type="hidden" name="business" value="payments@foo.com" id="id_business" />
    <input type="hidden" name="item_name" value="Standard" id="id_item_name" />
    <input type="hidden" name="a3" value="29.00" id="id_a3" />
    <input type="hidden" name="p3" value="1" id="id_p3" />
    <input type="hidden" name="t3" value="M" id="id_t3" />
    <input type="hidden" name="src" value="1" id="id_src" />
    <input type="hidden" name="sra" value="1" id="id_sra" />
    <input type="hidden" name="no_note" value="1" id="id_no_note" />
    <input type="hidden" name="notify_url" value="http://example.org/dashboard/payments/paypal/notify" id="id_notify_url" />
    <input type="hidden" name="cancel_return" value="http://example.org/dashboard/payments/paypal/cancel" id="id_cancel_return" />
    <input type="hidden" name="return" value="http://example.org/dashboard/payments/paypal/return" id="id_return_url" />
    <input type="hidden" name="cmd" value="_xclick-subscriptions" id="id_cmd" />
    <input type="hidden" name="charset" value="utf-8" id="id_charset" />
    <input type="hidden" name="currency_code" value="SGD" id="id_currency_code" />
    <input type="hidden" name="no_shipping" value="1" id="id_no_shipping" />
    <input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_subscribeCC_LG.gif" border="0" name="submit" alt="Buy it Now" />开发者_高级运维;
</form>

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The code is working fine. The issue was that I needed to create a business sandbox account, rather than using the regular PayPal email. I wish their error messages were a bit more descriptive.