I've managed to get my timesheet hours from TSheets into QB, but I can't now get them into my invoices as billable time.

Thanks for posting in the Community, @TomNouveauCare. I'm here to ensure you're able to get the timesheet hours into your invoices as billable time. 

The time data in Tsheets automatically syncs in QuickBooks Online (QBO). Since it doesn't work now, the billable feature associated with your customers or employees may haven't been enabled in QBO. That's why you're unable to see the timesheet hours into your invoices as billable time. 

To help fix this, let's either run the Time Activities by Customer Detail report for your customers or Time Activities by Employee Detail report for employees. From there, you can review if the customers or employees were marked as Billable or not.

Here are the steps to run the first report: 

1. Go to Reports from the left menu. 
2. Enter Time Activities by Customer Detail in the Search box. 
3. Set the Time Activity Date. 
4. Choose Run report. 
5. Locate the customer. 
6. In the Billable column, click No. 
7. Check the Billable(/hr) box and enter the rate. 
8. Select Save. 

The screenshot below shows you the last six steps. Just repeat the process above when pulling up the second report for your employees. 

Once done, log out and log back into your company. It refreshes the changes, and you'll be able to see the timesheet hours as billable time on the invoices. 

Aside from the reports above, I recommend running the other time tracking reports in the software. These will help you manage your timesheets and employee expenses. For more details, see the Access Time Tracking reports section through this article: How To Turn On And Set Up Time Tracking.

I'm always here to help if you need anything else. Enjoy the rest of your day, @TomNouveauCare.