Hello there, @mrc26.
There are limitations when switching companies from QuickBooks Desktop (QBDT) to QuickBooks Online (QBO). However, you're able to easily change the product type from service to non-inventory in QBO. After changing the product type to non-inventory in the Product/Service information page, I'd recommend selecting the Choose a special category option instead of the Nontaxable one directly. From the said page, you can select the Nontaxable option to update the product type successfully. Let me guide you how.
- Go to the Gear icon.
- Select Products and services.
- Find the service item you want to change, then select Edit under the Action column.
- Select the Change type hyperlink, then select Non-inventory.
- Go to the Sales tax category section, then select the Choose a special category option.
- In the Choose a special category page, go to the Standard categories section, then select Nontaxable.
- Click Done.
- Select the Save and close button.
I've attached a screenshot below that shows the last four steps.

However, in case the above steps didn't work, you can import a list of your non-inventory items to your QBO account. Then, merge them to the duplicate service items to keep your account updated. You can refer to this article for the step-by-step guide: Merge a product or service. It also includes a guide on how to reactivate a produce item.
Additionally, you can easily keep track of your product and service items in QBO. This gives you more detailed financial reports and helps you complete transactions faster. You can learn more about this through this article: Product and service items to QuickBooks Online. It includes topics about getting sales insights using reports.
Feel free to leave a comment below if you have follow-up concerns about updating product type in QBO. I'll be right here to help. Take care always.