If you've created a new contact in your accounting system and they aren't syncing into Pinch, sometimes the problem is that the accounting system doesn't know if that contact is a customer (vs being a supplier, etc...). Since we only sync customers to Pinch, the contact is therefore missing.
To resolve the problem in most cases, raise a sales invoice for the contact, and then try syncing again. This should create the contact as a Payer in Pinch.
As always if you still can't find the payer, get in touch with support so we can help out.