Good day, helen4.
Welcome to the Community. I'd be happy to help you route in the right direction to find your clients data in QuickBooks Online.
You may want to make sure that you are accessing the right account of your client. Once you verified that it's the correct account, I highly recommend reaching out our QuickBooks Online Support so they can retrieve your client's data in a secure manner and investigate this further.
Agents have the necessary tools, like screen-sharing to get you back up and running. You can get our most-up-to-date contact number here: https://quickbooks.intuit.com/community/Getting-Started/Get-help-with-QuickBooks-Online/m-p/185932.
Should you have any other concerns, please let me know. Have a good one.
