There are instances that an issue like this persists when the system encounters browser-related issues,  robert-ttproject. 

It's possible this might be caused by a corrupted file cache stored in your browser, that's why your costs in a project reflect zero.

We can do some troubleshooting steps to rule this out. Let's open your QuickBooks Online account in an incognito or private browser. This mode will not save your browsing history and will also help isolate any web issues. 

Here are the keyboard shortcuts:

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

If this works, it means that you need to clear the browser's cache so the system can start fresh. If you get the same result while using a private browser, you can also use a different supported browser as an alternate solution.  

You might also want to learn more about the Project feature in QBO. This article will provide some information on how to handle project transactions: Projects FAQ.

I'll appreciate if you can get back to me and share how it works. I want to ensure that this gets resolved. Have a great day!