Welcome to the Community. It's vital you're able to use QuickBooks without running into issues that prevent you from achieving your goals. Don't worry, I'll be glad to steer you in the right direction with this.
To get started, I'd like to start off by troubleshooting this issue to determine if it's a browser-related issue. Clearing cache and cookies is a great way to clean your browser allowing it to work more efficiently. Here's an article that shows you how to do that: How to clear cache and cookies. If this doesn't work, I suggest contacting our support team again so they can review the case you're referring to above. Here are our contact details:
Schedule a Callback or start a Chat: click(?) in the upper right in QuickBooks Online > enter "Contact support" > choose Contact Us > provide a brief summary > select Let's Talk > choose Get a callbackor Start a Chat.