Why is my Income not showing on my Income Statement in QuickBooks?
This issue has been around since I first started using Quickbooks (now QuickBooks Online) since the late 1990's. See this video for the steps in helping you correct the problem with your records. Be sure when you change your item to the proper income account and then go to the subsequent invoices to update them, you are careful to write down the amount that was originally in place. Changing the item will change your amount due. So when you change the item back to the newly coded one, you want to make sure you enter the correct amount that was originally on the invoice. For a step-by-step help video on setting up items and products in QBO, see this video from Intuit.