There are chances that the browser or system is configured poorly, Will. 

Before we proceed, may I ask which specific bank account you're trying to categorize? It will help us narrow down the possible cause of this issue. 

To avoid storing files, I recommend using a private browsing window. Browsers use cache and cookies to load web pages more quickly.

To open an incognito window, you can refer to these keyboard shortcuts:

• Google Chrome: Press Crtl+Shift+P
• Microsoft Edge & Mozilla Firefox: Crtl+Shift+N
• Safari: Press Command+Shift+N

After opening a private browser and you still have the same result, I suggest utilizing another supported browser. It will help us identify if the issue is specific to your current browser.

If you can categorize and split your transactions using another browser, consider returning to your regular browser and clearing its cache and cookies.

Moreover, let me share this article to help you set up your bank rules: Set up bank rules to categorize online banking transactions in QuickBooks Online.

Let me know if you still have questions about your bank transactions. Have a great day.