All of my customers and invoices has disserpeared.

Welcome, Rich. I'm glad to see you here.

Allow me to help you show your customers and invoices in their respective sections.

From the Sales tab, click the Customers option since nothing is visible, try to search for your customer name in the customer search field. Then, to your invoice transactions, click the Invoices tab and try to change the Status field to Needs attention, Unpaid, or Paid. 

Customers:

Invoices:

If nothing shows, try to refresh the page to trigger the system to display your customer lists and invoice transactions. Then, repeat the steps above. 

If you still can't see your customers and invoices, let's try to perform some basic troubleshooting. This will determine if this is a browser-related concern. The first is to access your QBO account through incognito mode. This doesn't store cache files that cause odd behaviors when running web-based programs. You can use the shortcut keys below:

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

Then, try to view your customer and invoice lists. If this works, clear the cache of your regular browser to remove the stored-up data. If the issue persists, you can use another supported browser or device. There's a possibility that the current one you're utilizing has a temporary issue with the program.

I'll also suggest contacting QBO support if the provided steps don't fix the issue. They can help you pull up your account in a safe environment and check the root cause of your concern.

To help you personalise and add specific info to your sales forms, you can read this article: Customise invoices, estimates, and sales receipts in QuickBooks Online.

For additional questions, don't hesitate to route back yourself here. The Community is willing to lend a hand. Take care always, and have a good day.