I have the same problem. I have checked the emails are correct. One of the customers is a world wide insurance company, so I'm thinking they wouldn't be the iss...
I'm in the same boat. Only for one customer who I send invoices to daily. Some send, some dont in the past week or so. Nothing has changed. They just dont send....
No, its the signature of receiving a payment in QuickBooks I send the customer to show I received it. It's OK though, I'll somehow remove the signature line.
