Update README.md

In response to issue iATSPayments#372, documentation of recurring failure handling.

README.md

@@ -109,6 +109,8 @@ Some issues may be related to core CiviCRM issues, and may not have an immediate
 
 Below is a list of some of the most common issues:
 
+Unexpected failures. If you get an unexpectedly large number of failures for your recurring contributions, please review this page to understand how the extension does it's best to handle them and what administrators can do: https://github.com/iATSPayments/com.iatspayments.civicrm/wiki/Recurring-Contribution-Failure-Handling
+
 9002 Error - if you get this when trying to make a contribution, then you're getting that error back from the iATS server due to an account misconfiguration. When this happens and your using a 'legacy' iATS account -> check if you have special characters in your password (and remove them). If you're using '1st Pay' contact iATS Customer Service to ensure your account is configured properly.
 
 CiviCRM core assigns Membership status (=new) and extends Membership End date as well as Event status (=registered) as soon as ACH/EFT is submitted (so while payment is still pending - this could be several days for ACH/EFT). If the contribution receives a Ok:BankAccept -> the extension will mark the contribution in CiviCRM as completed. If the contribution does NOT receive a Ok:BankAccept -> the extension will mark the contribution in CiviCRM as rejected - however - associated existing Membership and Event records may need to be updated manually.