Invoices were generated via Glue-Up and automatically generated in Quickbooks. I edited the customer account by adding the opening balance, but it does not want to save.

Hi there, -saiie-co-za.

Thank you for posting in the QuickBooks Community. I'll share details on how opening balance for a customer works in QuickBooks Online.

The method for entering opening balance to a customer depends on when you save their profile. That said, you can no longer add an opening balance in QuickBooks Online once the customer's profile is saved. Meanwhile, you'll have to manually create an invoice or customer credit in the QuickBooks system to have an opening balance.

Here's how to create an invoice:

1. Click the + New icon.
2. Choose Invoice.
3. From the Customer dropdown, select a customer. 
4. Enter the invoice date. Then, from the Terms dropdown, choose the due date.
5. From the Product/Service column, select a product or service.
6. Fill in the other necessary field.
7. Hit Save and close.

To see additional information, you can open this article: Create invoices in QuickBooks Online.

Please follow these steps on how you can create a credit note:

1. Go to the + New icon.
2. Select Credit note.
3. In the Customer dropdown, select the customer's name.
4. Enter the credit note details, such as the date and the amount.
5. When you're done, click Save and close.

You can click this article to view further details: Create and apply credit notes or delayed credits in QuickBooks Online. This also provides information on when to give a credit note or delayed credit to customers.

Please refer to this article to see various information on how the Sales page gives you a great at-a-glance view of the status of sales transactions, open invoices, and paid invoices: View sales transactions.

If there's anything else that I can help you with, please let me know in the comment section down below. I'll be always around ready to help.