Hello there prasanthsivaasn,
I want to make sure you're able to get back in business as soon as possible.
Are you getting this error in the QuickBooks Online application? If you access your account using a web browser, a web page page issue might be causing this error message to appear. Please perform the following steps below to isolate most common web page issues.
Otherwise, if you're using the application, reset the app by going to the Help menu and choosing Reset App Data.
If you get the same result, please contact our QuickBooks Customer Care Team. They have the advanced tool to take a closer look at the issue.
Please let me know if you get any success updating the invoice format. Thank you.