Thanks for reaching out to the Community, Rob - PRSM.
 

I appreciate you working with our Customer Care Team on this and trying their suggested troubleshooting steps. As mentioned by Rustler and my colleague, JamesDuanT, the categories feature is only available with a QuickBooks Online Plus subscription. If you're using any other plan, it won't be an accessible option.
 

Here's how to check your account and upgrade it:
1. Use your Gear (⚙️) icon, then go to Account and settings.
2. Open the Billing Subscription tab.
3. In your QuickBooks Online tile, select Upgrade your plan.
4. If you'd like to upgrade, choose a new plan. The one you're currently subscribed to won't be displayed.
 

If our Plus subscription wasn't being used previously and you've now switched to it, you can follow the steps provided by JamesDuanT to get started with class tracking.
 

You'll also be able to find many resources about using QBO in our help article archives.
 

If there's anything else I can help with, feel more than welcome to reach out anytime. Have a great Friday!