Why are not all transactions are automatically updated from bank account?

Try opening your QBO account on any private/incognito browser.

Heyu there Support_What_Support,

Thanks for reaching out to us here. QuickBooks Online is a great tool to have, It helps keep your books balanced. It's important that you're able to continue with your QuickBooks goals. I can provide some information. 

It may be browsing data on your system that is preventing the software from doing what it is supposed to do. Here are some steps to resolve issues that are caused by browsing data:
 

• Clear your browser cache if you're using a browser
• Try a browser if you're using the app
• Try a private browser window
• Try another browser type
• Make sure you're using a supported browser and system
• Reset your Internet or try on another computer or device
• Uninstall the QuickBooks Online App, and re install it.

If the issue persist, I recommend reaching out to the support team outside of the Community. They'll be able to verify your account details in a secure setting, as well as view your screen to better assist you. They also have the necessary tools to create a ticket to get the issue resolved if they see fit. You can reach them by following one of these methods:

Schedule a Callback or start a Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat.
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If you have any other questions, feel free to reach out here.