I'm trying to make a payment on a quote/order/invoice I am getting an error
You may encounter a scenario where the quote/order/invoice couldn't be synced to Pencil and therefore when a customer tries to make a payment it has an error.
Issue: The quote/order/invoice couldn't be synced to Pencil and therefore when you try to make a payment, an error comes up. Please see screenshot for reference;

The issue most likely is the Customer in Cin7 doesn't have INCLUDE IN EMAILS selected and therefore the sale order/invoice cannot sync to Pencil.
- You need to check the customer contact in Cin7, update it.
- Once you've updated the customer contact in Cin7, you can then go to Pencil → Sales Orders → resync the sale order/invoice number and it should show in Pencil → Sales Orders after a minute or two.