We are trying to send a quote and receiving the following error:

It is specific to the customer and I cannot figure out why. I thought maybe it was because they are in Canada, but that does not seem to be the issue.
I've tested--
Items-Different customer in US, same exact quote (no error)
Country-Different customer in CA, same exact quote (no error)
Confirmed email address
Confirmed Contact card in CRM
Customer-New quote, same customer, (error)
We found this online: https://msdn.microsoft.com/en-us/library/dd338605(v=nav.71).aspx
But I don't think it has anything to do with length in any fields in the contact or customer that I am aware of because we've sent out many quotes and invoices to other customers with no issues.
Anyone else come across this error, or have any input?
Thanks!