Hello ! I totally understand you all's frustration with your payments not processing with sales receipts. In case no one has given you an update. In Quickbooks Online, Auto pay is processed on recurring invoices only. automatic payments from your customer are no longer supported on recurring sales receipts. I have provided an article below to help your customers setup autopay.  I hope this helps.  

Set up Autopay for recurring invoices in QuickBooks Online.
https://quickbooks.intuit.com/learn-support/en-us/help-article/invoicing/set-autopay-recurring-invoi...