Thank you for reaching in the Community, @Sherrinotafan.

I understand how you feel when something isn't working in QuickBooks Online. I am here to let you know that this error has been resolved by our engineers. If you're still getting the same behavior, let's clear the app's data to refresh the connection.

To start, let’s log in to a private window and access your account there. This way, you'll know if it's your browser that’s causing the error.

Here are the keyboard shortcuts:

• Google Chrome: press Ctrl + Shift + N.
• Mozilla Firefox: press Ctrl + Shift + P.
• Internet Explorer: press Ctrl + Shift + P.
• Safari: press Command + Shift + N.

If you can successfully isolate the problem, proceed to clear the cache. Clearing cache and cookies will also help improve your experience in navigating your account. The following link will walk you through the steps: Delete or Disable Cache and Temporary Internet Files in Your Web Browser.

Once it work's fine as suggested, let's proceed to the workaround provided by my colleague above then try to add the attachment again.

Please let me know how it goes or if you need further assistance. I'll be around to help. Take care!