Paypal instant payment warning

I got this email from pay pal. Can you tell me what to do *****

Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) are failing:

https://app.funnelish.com/apps/api/v1/ipn

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. If this problem continues, IPNs may be disabled for your account.