Can adv why my product category data lost after adjusted the stock qty ?

Hello there, @joannaneo1.

I can provide some clarification about adjusting inventory in QuickBooks Online.

Entering inventory quantity adjustment will not make any changes to your existing information. It may be possible that the category was altered unintentionally in your QuickBooks company.

I recommend you visit the Audit log section to keep track of any user activities. If the data is removed or deleted, it should reflect from the Event column along with the name of the user (see screenshot below).

If there are no changes, I suggest you proceed with creating a new product category and inventory adjustment. This way, we'll be able to determine if it affects the existing information.

I've included an article you can use to handle product and service items, like how you can edit them in QuickBooks: Add product and service items to QuickBooks Online.

If you have additional questions or concerns while working in QBO, leave a comment below. I’ll be happy to help you out.