I received a payment notification email but the payment did not post to the invoice or shows in Quickbooks. Has this ever happened to anyone else? What does it mean?

I'm glad you've found your way to the Community, infosignaturedan.

Let's get this sorted out so the payment will show in QuickBooks Online (QBO).

Let's try to check if the payment has already been deposited by logging into your Merchant Service account. I'd be happy to show you how. Please follow the steps provided below:

1. Log into the Merchant Service Center.
2. From the top menu, click Activity & Reports.
3. Click Transactions.
4. Select Card (credit card) as the transaction type and a date range. 
5. Click the Trans ID number to display a detailed view of the transaction. 

If you confirm that it's already been deposited, I recommend getting in touch with our Merchant Support Team so they can take a closer look as to why these payments are still not showing in QuickBooks Online.

If there's anything else you need or questions about QuickBooks Payments, just let me know as I'm here to help.