Paypal 沙盒测试 - 更改 URL 端点?

It seems there are a lot of changes with Paypal Sandbox lately and I am stuck with my testing. Before, we only point to https://www.sandbox.paypal.com/cgi-bin/webscr for Sandbox testing as seen in the code below:

<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" style="padding: 0; margin: 0;">
<input type="hidden" name="cmd" value="_xclick" />
<input type="hidden" name="business" value="your bussiness id" />
<input type="hidden" name="quantity" value="1" />
<input type="hidden" name="item_name" value="your item" />
<input type="hidden" name="item_number" value="1" />
<input type="hidden" name="amount" value="item price" />
<input type="hidden" name="shipping" value="0" />
<input type="hidden" name="no_note" value="1" />
<input type="hidden" name="notify_url" value="Your notify url">
<input type="hidden" name="currency_code" value="GBP" />
<input type="hidden" name="rm" value="2" >
<input type="hidden" name="return" value="your return url">
<input type="image" border="0" name="paypal" src="images/btn_paypal_nl.gif" onClick=""/>
</form>

但现在，Sandbox 不断要求我请登录以使用 PayPal Sandbox 功能".我认为这意味着鉴于最新的 Paypal Sandbox 更改，我使用了错误的端点.