This could be a browser related issue, joylamsihk.
Let's perform a few troubleshooting steps to resolve this.
Please try logging in to a private browsing window and see if you still get the same error.
If it works, kindly go back to your main browser and clear your browser's cache. Please check this article for your reference: https://quickbooks.intuit.com/community/Getting-Started/How-do-I-clear-my-browser-cache-and-temporar....
If it doesn't work, you can also try using a different browser to create an invoice.
Please feel free to comment below if you need more help.