Let's make sure to fix the error code you're getting, shaunie-whynters.

Normally, you'll get this error when you're trying to upgrade or if there's anything to do with your credit card transactions. However, there are also times that your browser is full of frequently accessed page resources that cause some unusual responses that's why you're getting the error. You can perform some troubleshooting steps to isolate this issue. You can log into your QuickBooks Online (QBO) account in a private window (incognito). Here's how:

• Press Ctrl + Shift + N (Google Chrome).
• Ctrl + Shift + P (Firefox).
• Control + Option + P (Safari).

Once signed in, you can try upgrading your subscription. If you're able to do so, return to your default browser and clear the cache to speed up the loading process. Every so often the cache becomes overwhelmed with older data which can potentially cause viewing and performance issues. Clearing it will refresh the system, and you'll be able to work with a clean slate. If the issue persists, use other supported browsers. 

But If you're still getting the error, I recommend reaching out to our support team so they can double-check what's causing the error. They have the tools to pull up your account securely and investigate further. Here's how to reach them:

1. Click the (?) Help icon and enter Talk to a human (then type it again when prompted).
2. When asked by the bot, enter your concern.
3. Select I still need a human, then proceed with Contact us or Get help from a human.
4. Choose either Chat or Callback.

Furthermore, QuickBooks Online (QBO) provides dozens of reports that tell you the different aspects of your business. Learn how to customise them so you'll get the data you need. I've got this article for your guide: Customise Reports in QuickBooks Online.

Feel free to let me know if you have any concerns about the upgrade. I'll always be right here to assist you.