If you have invoices that were paid and they show as paid in MYOB but they do not show in Pencil, the usual cause for this type of issue is that the MYOB integration has been disconnected from Pencil.
To resolve this, you can go to https://support.pencilpay.com/knowledge/how-to-connect-your-myob-account-to-pencil you may need to disconnect MYOB first by toggling OFF the green switch in the top right and then reconnecting MYOB.
This may solve most of your issues that shows invoice as Paid in MYOB but not in Pencil and the same is true vice versa (Invoice shows Paid in Pencil but not in MYOB).
If you want to repush the payment to MYOB, follow these steps: How do I re-push a payment from Pencil to my accounting software (pencilpay.com)