You could also try these steps from knowledgebase article ID:14025.

Before trying any of these steps MAKE A NEW BACKUP! If something goes wrong, restoring a backup is often the only way to undo the effects.

Section I: The Amount Paid on the invoice has a negative amount

1. On the receipt that pays the invoice uncheck the Pay box for the invoice in question
2. Recheck the Pay box for the same invoice
3. Verify the receipt now has a positive amount
4. Click Save

Section II: Delete and recreate the entries

1. Delete the receipt and then the invoice following Article ID 10834: How to delete a transaction
   Note: If the invoice cannot be deleted, skip to Section III below.
2. Reenter the invoice.
3. Reenter the receipt.

Section III: Run the Integrity Check, Invoice/Payment Sync Tests

• Run the Invoice/Payment Sync Test and select Accounts Receivable. See Article ID 10147: How do I run the Invoice/Payment Sync Test for Accounts Receivable?

Section IV: Unpost all journals and run Data Verification

1. Unpost all journals. See Article ID 14900: How to unpost and repost journals
2. Perform the Data Verification test. See Article ID 10788: How do I load, access, and run Data Verification?
3. Verify the invoice is corrected.
4. Post all journals again, or change the posting method to Real-Time. See Article ID 10138: How can I change my company's posting method?

You could also try these steps from knowledgebase article ID:14025.

Before trying any of these steps MAKE A NEW BACKUP! If something goes wrong, restoring a backup is often the only way to undo the effects.

Section I: The Amount Paid on the invoice has a negative amount

1. On the receipt that pays the invoice uncheck the Pay box for the invoice in question
2. Recheck the Pay box for the same invoice
3. Verify the receipt now has a positive amount
4. Click Save

Section II: Delete and recreate the entries

1. Delete the receipt and then the invoice following Article ID 10834: How to delete a transaction
   Note: If the invoice cannot be deleted, skip to Section III below.
2. Reenter the invoice.
3. Reenter the receipt.

Section III: Run the Integrity Check, Invoice/Payment Sync Tests

• Run the Invoice/Payment Sync Test and select Accounts Receivable. See Article ID 10147: How do I run the Invoice/Payment Sync Test for Accounts Receivable?

Section IV: Unpost all journals and run Data Verification

1. Unpost all journals. See Article ID 14900: How to unpost and repost journals
2. Perform the Data Verification test. See Article ID 10788: How do I load, access, and run Data Verification?
3. Verify the invoice is corrected.
4. Post all journals again, or change the posting method to Real-Time. See Article ID 10138: How can I change my company's posting method?

It will not allow us to view the entered transaction at all.