We acknowledge the need to get this issue resolved, @Wimberly05.

QuickBooks Online automatically applies the customer's existing payment from the previous transaction to their new invoice. That explains why your newly created Invoice gets marked as paid. 

First, we can turn off the Automatically apply credits. Here's how:

1. Go to the Settings ⚙.
2. Choose Accounts and Settings. 
3. On the Advanced tab, select Automation.
4. Under Automation, toggle off the Automatically apply credits.
5. Then, Save. 

Next, delete the payment linking between the Invoice and the existing payment. Here's how: 

1. On the left navigation panel, click Sales. 
2. Under Invoices, select the specific Invoice transaction (the one that gets paid automatically). 
3. Click Edit.
4. Hit the "1 payment made.." and then, the date.
5. At the More menu, select Delete.
6. Then, Yes to confirm. 

Now that the Invoice isn't marked as paid anymore you can send it to your customer already. 

Normally, these steps are expected to work but it the issue persists it would be best to contact QuickBooks Online Support.

You can also check these articles for more insights:

• Create and apply credit memos or delayed credits in QuickBooks Online
• Send invoice reminders automatically or manually in QuickBooks Online

Feel free to visit the Community again if you have further queries. We are happy to help. Keep safe and have an amazing day.