I appreciate you getting back to us, Alexandra54.

Since the troubleshooting steps that they've provided didn't work, I'd recommend calling our QuickBooks Online Support to have this investigated.

Unlike in this public forum, they have the tools required to perform any escalations in the system whenever necessary on your behalf.

In the meantime, as a workaround, you can manually remove the credits by unchecking them when recording an invoice payment.

Please be reminded that our Support Team is available from 6:00 AM until 6:00 PM on weekdays, and from 6:00 AM till 3:00 PM  PT on Saturdays. Here's how to contact us:

1. Click the Help (?) icon.

2. Choose Contact Us.

3. Enter a  brief description of your situation in the What can we help you with? area, then click Let's talk.

4. You'll be presented with a few options for connecting with Intuit. Select Get a call.

You might want to visit the following write-up: Sales and customers. This will provide you links on how to manage your company income as well as sales in QuickBooks Online.

Keep me posted if there's anything else you need. I'll be here to provide additional assistance. Have a great rest of your day.