Let's make sure your desktop app is updated, @AlanR157.
If you accessed TSheets via QuickBooks Online app, let's clear the Windows App's cache to remove its stored data.
Here's how:
Go to the Help menuon the navigation bar at the top.
Choose Reset App Data.
Allow a moment for the process to complete, and then close the app.
Be sure to right-click the app and Run as Administrator when re-opening.
If resetting the App Data still doesn't make a difference, I suggest uninstalling and reinstalling the program. The steps below will help you accomplish this:
The method for uninstalling the App varies based on which version of Windows you're using. Refer to the QBO Windows App Help Guide under the How do I uninstall? section.
Once uninstalled, you'll still need to delete the locally stored settings.
Look for the QuickBooks folder. If you see a Roaming folder instead, open it first. Right-click and Delete the QuickBooks folder.
Using the guide in Step 1, under the How do I install the app? section, re-install the QBO app based on the instructions for your version of Windows.
However, if you are using a separate app, make sure it is up-to-date and also try to uninstall and reinstall it.
Additionally, I've also added articles about integrating sheets into QBO, timesheets management, and other relevant matters.