Why aren’t products adding to my invoices/estimates when i click on the column? I get the sidebar as if i am adding a new item when i click on an existing product

I am having the same issues, have been for a few days now.

Hello there, belinadesigns. Welcome to the Community space!

Once there's an existing item created, you should be able to add it directly on the invoice or estimates. When you click the drop-down menu, you'll see the list of products you want to use for the transaction. Please take note that you still have an option to create a new one from there. 

In this case, we can troubleshoot this one and identify if this behavior is causing by having too much cache in a browser you're using. You can start by accessing your QuickBooks account in a private/incognito browser.

Feel free to use these shortcut keys:
 

• Google Chrome: Ctrl + Shift + N
• Safari 11 or newer: ⌘ + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P

Once you're in, go back to your invoice or estimates. If it's working fine, we'll have to go back to your regular browser and clear the cache to eliminate the junk files. You can also use other supported browsers as an alternative.

In your free time, feel free to read these handy articles for additional reference:

• Set up product and service items you buy and sell.
• Set up and send progress invoices in QuickBooks Online. 

Don't hesitate to post again if you still need help or have other questions about QuickBooks. I'm more than happy to answer it for you. Have a great day.

It does work when I am in incognito mode. I have cleared my cache and it still doesn't work in my usual browser. What's next?

Hi there, JoyD.

I appreciate your time and effort in doing all the basic troubleshooting steps adding the product to your invoice.

For further assistance, it would be best for you to contact one of our QuickBooks Online Support.

Here’s how:

1.   Sign in to your QuickBooks Online company.
2.   Select Help (?) at the top right.
3.  In the search field, enter the topic you need help with. You can also enter questions.
4.  Click Contact us to connect with a live support agent.

Looking forward to your response. Have a great day!