Hi there, @ultrashine77.
Let's take a few steps together to troubleshoot and recover your customer records and invoices in QuickBooks Online (QBO).
To start, let's reload the page by clicking the Refresh icon, pressing F5 (on Windows), or Command-R (on Mac).

Once refreshed, check to see if your data reappears. If the issue continues, please log out of your account. Wait a few moments, then sign back in.
Please don't hesitate to leave a comment below if you have any further questions. I'm here to help.