I'd be delighted to walk you through the steps of finding the inactive account and making it active in QuickBooks Online (QBO), @nebbistudios.
You can simply navigate to the Chart of Accounts menu including the inactive accounts to make it active. Follow these steps to proceed:
- Go to the Transactions menu and select Chart of Accounts.
- Tap the small gear icon near the print icon.
- Place a checkmark in the Include inactive checkbox.

- Locate the Inactive account on the list.
- In the ACTION column, click Make Active.
You can refer to this article for more details about this process: Add and manage customers in QuickBooks Online.
For additional reference, I've attached a link you can use to learn more about how the chart of accounts works: Understand the chart of accounts in QuickBooks.
Ping me up if you need more assistance in managing chart of accounts in QuickBooks. I'm always here to help.