Thanks for joining this thread, @Marfa. I'm here to assist you in changing the income account for your product or service items.

It's important to note that you can only change the account for an item once. 

Since your past transactions aren't updating even after checking the Also update this account in historical transactions box, you can change the income account and then switch it back to the correct one. 

Additionally, if you're changing the income account while opening a report, you can close the report and reopen it to check if the modifications were applied.

If the same thing happens, you can perform some troubleshooting steps. A cache-related issue is likely causing the situation. You can use a private or incognito window to rule out cache problems in your browser. Here are the shortcut keys:

• For Mozilla Firefox browser: Ctrl + Shift + P
• For Google Chrome browser: Ctrl + Shift + N
• For Safari browser: Command + Shift + N

After that, you can log in to your QuickBooks Online (QBO) account and change the income account of your item again. If it works, you can clear your browser's cache. This removes the webpage data that's causing the issue. If a private browser won't work, you can use other installed supported browsers.

Moreover, you can use this article as a guide to changing the income account for your items: Change the account for a product or service item in QuickBooks Online.

In case you want to organize your products and services, you can check out this article for more guidance: Group products and services into different categories in QuickBooks Online.

I'm still ready to back you up if you have any other concerns besides changing the income account of your items. Feel free to leave a reply to this thread. Have a great day!