I appreciate you trying the recommendation provided by my colleague, mgiampietro.

The time to convert the billable expenses to non-billable will depend on how many transactions are being processed.

To verify if this is completed, you can run and customize the Uninvoiced Charges report.

1. On the left menu, click Reports.
2. On the search field, enter Uninvoiced Charges.
   
3. Customize the date period. 
4. Click Run report to refresh the data.
5. Click the Save customization button if you wish to memorize the report.

Moreover, if you get the Something’s not quite right. Please wait while we are converting Billable Expenses to non-billables.psng534 message again when running the tool, you can open your QuickBooks Online account in a private browser or Chrome's incognito window. This is a feature in the web which allows you to browse without storing any data history. 

Here's how to open a private window:

• For Internet Explorer or Firefox, press Ctrl + Shift + P. 
• For Chrome, press Ctrl + Shift + N.
• For Safari, hold down Command + Shift + N.

If this works well, you'll need to go back to the main browser and clear its cache. This will boost the performance of your browser and the application as well. 

Keep me posted on how these steps work out for you. I'll be glad to help you some more if need be. Have a good one.