AP Account 1 GL Number (00000-00) is In-Active in Fiscal Year
After closing your fiscal year, this error may display when you first process your Account's Payable Transactions. Sometimes creating next year's accounts in the Bookkeeper's Assistant Routine, the Accounts Payable Account gets cleared in Preferences. Thankfully, it's an easy fix.
Go to File, Preferences, Accounts Payable and Click the AP Account Button. Then select the GL Account Number you use for Accounts Payable.