Paypal isn't processing JotForm's IPN

I tried to do this and immediately got an email from Paypal that says:

Please check your server that handles PayPal Instant Payment Notification (IPN) messages. Messages sent to the following URL(s) are not being received:

https://www.jotform.com/ipns/paypal.php

If you do not recognize this URL, you may be using a service provider that is using IPN on your behalf. Please contact your service provider with the above information.

Once you or your service provider fix this problem, you or your service provider can resend the failed messages from the IPN History page. If this problem continues, PayPal may disable the IPN feature for your account.

Thank you for your prompt attention to this issue.

Now what do I do?  I need to be getting these submissions and I'm not.

The IPN URL is working fine. Can you please try it again?

May we also know the steps you've taken why you're getting this error? Did you enable the IPN in your Paypal account and set that URL?

May I also suggest checking the Paypal FAQs here to understand more about IPN, how to add them in your account and how to resend failed payments in your Paypal payment history http://www.jotform.com/help/272-Paypal-Incomplete-Payments-FAQ.

Let us know if you continue to have this error.