I am trying to add new product catogaries and the system is telling me that they already exist, however they are not displaying on my catogory list at all. what to do?

I'll make sure you can add new product categories in QuickBooks Online (QBO). 

We can perform some troubleshooting steps to fix this. There are times when the browser is full of frequently accessed page resources, which causes some errors or unusual responses. 

Let's start accessing your account using a different or private browser. You can use either of these shortcut keys:

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

Once logged in, try to add the product again. If it works, I recommend clearing your browser's cache. Doing so will remove the historical data and access QuickBooks with a clean slate. You can also switch to a different supported browser.

I've added these article to learn more about bringing in your data as well as managing products and services:

• Common questions about importing data
• Add stock products
• Group products and services into different categories

Come back to this post if you have other concerns or follow-up questions about products and services.  I'll be right here to help.