At the bottom of each invoice it used to show when the invoice was sent and opened by the customer. This has disappeared. How do we get this feature back?

I understand the importance of tracking the status of the invoices you've sent to your customers, @wellnesssaunas-g. Let me help and give you some steps that help resolve this matter.

To begin, you'll want to ensure that your invoices are set to Online Invoice. Here's how you can do that:

1. Go to the Gear icon, and click on Accounts and Settings.
2. Click the Sales menu.
3. Locate and click on the Online Delivery section.
4. Click the dropdown below Additional email options, and choose Online Invoice.
5. After making this selection, be sure to click Save, and then select Done.

If you're still experiencing issues after doing the steps above, you can use a private browser to rule out any browsing history or cached files causing the problem. Here are the shortcut keys for accessing private browsers:

• Google Chrome: press Ctrl + Shift + N
• Mozilla Firefox: press Ctrl + Shift + P
• Microsoft Edge: press Ctrl + Shift + N
• Safari: press Command + Shift + N

You can also clear your browser's cache and cookies, and use other supported web browsers that can help identify if the issue is related to your current browser.

If you're still unable to see the status of your invoices, I recommend reaching out to our QuickBooks Online Support since they have the expertise and the necessary tools to help you further. 

In the meantime, you can check the status of your customers within the Sales menu by following these steps:

1. In your left navigation panel, select Sales.
2. Click on Invoices.
3. Choose an invoice. 
4. Within your invoice, you can view the Invoice activity.

Furthermore, you can use this article to learn how to receive and record invoice payments: Record invoice payments in QuickBooks Online.

If you have further questions regarding invoices or anything related to QuickBooks, you're always welcome to comment down below. I'm always here to help you.