Thank you for providing a screenshot of your concern, @rcaccamisi. I've got here a few steps to ensure you can open your QuickBooks Online (QBO) account.
There are times that the web cache in your browser can interfere in accessing frequently visited websites such as QBO. Thus, running a private mode can help us determine if it is a browser-related issue. To start, let's run your QBO account using incognito mode.
To open a private browser on your iMac, you can press the Command + Shift + N keys.
Once done, sign in to your QBO account. If this works, you'll have to go back to your regular browser and clear the cache. If the same thing happens you can also open your QBO using another supported browser.
Should you need any handy sources that you can bookmark for future use, you can visit our QuickBooks Online Help page. The site has tons of help articles and even video tutorials that will be able to guide you on your QBO tasks.
If you have any other concerns about accessing your QBO on iMac, feel free to post a reply below. I'm always around to assist and ensure your success. Have a good one.
