How do I add to my product and services category. It only has non-inventory and services

You need to have QBO Plus or Advanced to manage inventories.

I'm here to assist you today. 

The Inventory feature is only available in QuickBooks Online (QBO) Plus and Advanced. If you're using either one of them, ensure that the feature is enabled for you to see the Inventory option. Here's how:
 

1. Go to the Gear icon and click Account and Settings.
2. Under the Sales tab, click the Pencil icon in the Products and Services section.
3. Check the box for Track inventory quantity on hand. This will enable you to select Inventory when creating a new item under Products and Services.
4. Click Save.

However, if you're using Simple Start or Essentials, you might consider upgrading your QuickBooks Online subscription to activate this feature. If the same thing happens, try logging in to your account using a private browser to single out the cause of this unexpected behavior. You may use either of these shortcut keys to access your account using a private browser: 
 

• Google Chrome, press CTRL  + Shift + N
• Mozilla Firefox: press CTRL  + Shift + P
• Safari: press Command + Shift + N

If it works fine, access your account using the original browser and clear the browser's cache. The overtime collection of data can create corruption, however, removing this should fix the issue. You can also use supported, up-to-date browsers to roll out the possibility of a browser-related issue.

However, if you don't have the QBO Plus or Advanced plan, you'll want to upgrade your QuickBooks plan to start tracking your inventory.

In case you need reference about adding inventory products in QuickBooks Online, feel free to visit this link.

Keep in touch if you have further queries about importing products as inventory type in QBO. Just leave a reply below, and I'll get back to this thread to answer them. Stay safe, and have a good one.