If the journal entry was a credit to cash and debit to accounts payable, then you need to clear the AP invoices without changing the GL. You can do that by recording a payment against the invoice like you normally would EXCEPT you need to change the cash account to your accounts payable account. That way the same account will be debited and credited so it's balance won't change.

Sage 50 always remembers the last cash account that was used. So after you do this, it's a good idea to open an existing transaction that uses your regular cash account and save it. That will reset cash account so the next person won't accidentally post checks to the wrong account.

This method worked for closing out the vendor invoices and correcting the COS. The trial balance is still out. Will adjusting the beginning balance of the GL account bring it into balance?

When you say "The trial balance is still out" do you mean the accounts payable account on the trial balance doesn't agree with the aged payables report, or do you mean the debits and credits on the trial balance don't balance?

Trial Balance Debits & Credits do not balance.

Follow these steps from Knowledgebase ID:11141 . They will get your trial balance back in balance.

Section I: Check for Damaged Transaction Errors

1. Click Reports & Forms, General Ledger
2. Select the General Ledger report
3. Click Options
4. Change Time Frame to All
5. Click OK
6. If no error appears, skip to Section II; if an error does appear, continue to the next step
7. Close the error message, the General Ledger report, and Select a Report or Form
8. Have all other users close Sage 50
9. Click File, Data Verification
10. Leave Both tests selected and click Start
11. Save the backup; the tests will begin automatically when this completes
12. When the Data Verification has finished, check the account balances; if still incorrect, or if the General Ledger Trial Balance and/or Balance Sheet are out of balance, continue to Section II

Section II: Integrity Checks

Note: It is recommended to make a backup of the company prior to performing these steps.

1. Have all other users close Sage 50
2. Select Tasks, System, and then select Change Accounting Period
3. Select period 01
4. Click OK
5. Select Help, Customer Support and Service, and then select Integrity Check

Note: If using Peachtree 2012 or older, refer to Article 12115 (How do I access the Integrity Check in prior versions?) in the Related Resources section.

1. Run Chart of Accounts/Journal Synchronization test, refer to Article ID (How do I run the Chart of Accounts Journal Synchronization test?) in the Related Resources section 
2. Check the account balances the General Ledger should now be in balance if the account balance is still incorrect, proceed to the next step
3. Access Integrity Check, and then click Continue 
4. Select Journal Balances box, and then click OK
5. Access Integrity Check, and then click Continue
6. Select G/L Balances box, and then click OK

Thank you for the information. Will check and update thread.