Thank you for posting in the Community. I'm here help share some information about invoice statuses in QuickBooks.
The status of an open invoice will change to Sent after sending the invoice. It will only change as Viewed if the customer opened the invoice emailed to him. Here's a sample screenshot.
It's unusual if the customer opens the emailed invoice but still showing as Sent in the Status column. Let's try checking if this is a browser's issue by logging in to a private browser. You can follow the shortcut keys below depending on the browser you're using:
Google Chrome: press Ctrl + Shift + N Mozilla Firefox: press Ctrl + Shift + P Internet Explorer: press Ctrl + Shift + P Safari: press Command + Shift + N
Thanks for bringing this concern to us. As my colleague stated above, it's unusual if your customer opens the emailed invoice but still showing as Sent in your Status column and not Viewed.
To get this sorted out, I recommend performing basic browser troubleshooting tests. This way, we can check it if this a browser related issue. For the detailed steps, please refer to the steps provided by my colleague @LilyC above.
Then, if you're able to see the Viewed status of the invoice in your Status column, you'll have to clear your browser's cache. Stored data overtime can cause unusual behavior to your browsers, clearing cache once in a while optimizes your browser performance.
Also, feel free to visit our Income and expenses page for QuickBooks Online to learn some tips on managing your invoices and expenses.
As always, visit our Help articles page in case you want to learn some "How do I" steps in QuickBooks Online.
Don't hesitate to reach out to us if you have other concerns regarding your account. We're always here to help.