Hello TraderJohn300,

Welcome back to the Community!  An error like this can be triggered by random browser issues. So let's start by doing some basic browser troubleshooting steps to fix this.

You'll want to sign in to QuickBooks using a private browser. This step disables its extensions and stops the cache from saving your browsing history.

• Google Chrome: Ctrl + Shift + N
• MS Edge and Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

If you do not notice the error when voiding the invoice, you need to go back to your regular browser and clear its cache. However, if it still keeps on popping up, please try other browsers and let me know the result.

I will be here, ready to assist further. See you soon.