It's important that you can monitor your sales transactions. I'm here to help you out. By the way, are you experiencing this in the mobile app, desktop app, or in the browser interface?
Let's check to see if you have an active filter on your Sales Transactions page. If there is, simply click on Clear Filter / View All.
If you never use any filters at all, we'll do some troubleshooting steps to see if a browser issue causes this behavior. We'll start by signing in to QuickBooks using a private browser. This step disables its extensions and stops the cache from saving your browsing history.
Google Chrome: Ctrl + Shift + N
MS Edge and Firefox: Ctrl + Shift + P
Safari: Command + Shift + N
If you can see your sales transactions, you'll want to go back to non-private browsing and clear your cached data. If it's the same thing, please try other browsers to isolate the case.