Welcome to the Community forum, @Eric the Red. I can share some information about why your invoices show as paid when they're not. 

The possible reason why the invoice was marked as paid is that the Automatically apply credits feature was on. This feature will automatically apply payments to the new invoice and tag it as paid if your customer has a credit balance.

To fix this, let's turn off the feature to avoid this from happening in the future. Here's how:

1. On your QuickBooks Online (QBO) account, click the Gear icon.
2. Select Account and Settings.
3. From the left menu, click Advanced.
4. Go to the Automation section.
5. Toggle the Automatically apply credits option to turn off.
6. Click Save, then Done.

After that, let's open the invoices and delete the applied payment. This way, the invoices will be open again.

Let me show you how:

1. On your QuickBooks Online (QBO) account, go to the Sales menu at the left pane to get to the Invoices page. 
2. Click the invoice to open and tick the 1 payment made hyperlink below the PAID status.
3. Choose the date, then remove the checkmark to the invoice to unlink the payment in the Receive Payment screen.
4. Click Save and close.

To learn more about receiving payments and applying credits in QBO, see these links:

• Record invoice payments in QuickBooks Online
• Handle a customer credit or overpayment in QuickBooks Online

Just in case you'd want to return your customer's money, here's a great article that you can read for more guidance on what to do: Record a customer refund in QuickBooks Online.

Please let me know if you have any other issues or concerns by leaving a comment below. I'm more than willing to assist. Have a great day!