We'll check to see it's a browser-related issue, emsvc.
Let's start with some basic QBO troubleshooting steps. Please switch to an Incognito window. Just press CTRL+SHIFT+N.
If you're able to edit the class, you'll want to clear the browser's cache. It helps us get rid of the stored files in your browser. Using a different browser can be an option, too.
Please give us a call if you're still can't change the class.
I'll be here if you have any further concerns.