Edit on general journal entry says when you use A/P you must choose a vendor in name field. I did so but it won’t save and keeps giving that edit. What can I do?

I'm here to make sure you can save your journal entry successfully, @goodwinfarms.
 

For any line in a Journal Entry (JE) that you've posted to an account that is Accounts Receivable (A/P) or Accounts Payable (A/R), you must specify a Customer name or Vendor name.
 

These messages appear when the A/R or A/P account is chosen on a transaction but the name associated with that account is not a customer or vendor name, respectively. It's also possible that the vendor's name isn't in line with the A/P.  See the screenshot below for your reference.

I'm also adding these articles to learn more about recording journal entries, as well as managing your Chart of Accounts:

• Create a journal entry in QuickBooks Online
• Understand the chart of accounts in QuickBooks

I'm always here to help if you need further assistance in entering a journal entry. Have a good one.