Thanks for posting here, @CJ_Aus,

I want to share some information about this error you're getting. This is usually caused when QuickBooks is unable to connect with your bank because of undergoing maintenance or have server issues.

To resolve this, try refreshing the bank connection. Use the Update button to sync bank transactions into the system automatically.

Next, sign-in to the bank website and see if there is an ongoing maintenance. We need to make sure everything is working on their end.

1. If you're unable to sign in, reach out to your bank or credit card company about next steps.
2. Look for any messages, notifications, or alerts. These should tell you if something isn't working.
3. Review your account pages, account history, and transactions. If you can't see these, there may be connection issues.

See this link to learn more about the error 105 and how to fix it: Connect bank and credit card accounts to QuickBooks Online

Let me know what happens after trying out the steps. I'll be waiting for an update from you so I can help you further anytime. Have a good one!