When in a invoice why can't I change the quantity line

Hi there, @veteransplumbing1.

I'll share some information regarding this query with invoices in QuickBooks Online (QBO). I'm here to ensure you get routed in the right direction for support.

At the moment, we've received similar cases or reports from other users about the issue. I suggest contacting our support so they can add you to the affected users list. Here's how:

1. From the Search tab, click Contact Us.
2. Enter your question and select Continue.
3. Review and choose from the following: Have us call you or Chat with us.

A workaround I can suggest is to access your QBO account using your mobile app and try changing the quantity line of the invoices from there.

Additionally, a detailed process is laid out in this article to account for your customer's payments moving forward: Record an invoice payment. It includes a visual reference for an additional guide.

Fill me in if you have more queries with invoices or any transactions in QBO. I'd be glad to assist you further. Take care always and best regards.