Why project or customer in my qbo is not appearing I can't link my expense , purchase order etc. to it's respective projects?

Let's run some troubleshooting steps to fix this concern,  jennelyn-samulde.

To start with, let's open QuickBooks on a private window. It is the best place to identify any browser-related issues. You can use these keyboard shortcuts to open one:

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

If it works, you can go back to a regular browser and clear its cache. A piled cache can also be the reason for some unexpected error on the opened pages.

You can also switch to a different browser like  Google Chrome, Mozilla Firefox, Safari, or Microsoft Edge as alternative.

I've also added these references about projects: Set up and create projects in QuickBooks Online.

Let me know these steps work on your end. Keep safe!