can't attach document to invoice

I can see this has been a challenging task for you to do, @JesusChrist. Let's team up to resolve this error you experienced under the invoice section in QuickBooks Online.

We received an update about the attachment issue within the invoice that's been resolved by our team. Since you mentioned that you encountered the same issue, we encourage you to call our support team so our QuickBooks Support team can look further into your account and provide remedies to the error.

Follow the steps below:

1. Log in to your account.
2. Click the Help button at the top right corner.
3. Go to the Search tab, then select Contact Us.
4. Enter a brief discussion with your concern, then click Continue.
5. Choose to Have us call you to connect with us.

Furthermore, to learn more about using QuickBooks Online, managing your account, and handling invoices and subscriptions, visit this article for additional references: Manage billing, payment, and subscription info in QuickBooks Online.

We are here to support you again if you need to customize your invoice in QuickBooks Online. Let know if you have concern. Have a nice day.