Thanks for joining the Community, hello262. I can definitely understand the situation and am here to help with your bank connection.
To verify my understanding of what you're experiencing, when your accounts won't link and it says Westpac has lost connection, do you see any error messages or codes displayed? If so, it'd be helpful if you could provide a screenshot of what you're seeing. Any information helps.
I'd also like to confirm which Intuit product(s) you're using, such as QuickBooks Online (QBO), or QuickBooks Desktop (QBDT), as well as the version in use (United States, Australia, etc.). Once I have this info, I can do further research on my end and see what I can find out for you.
If you're using the US version of QuickBooks Online, I've included a couple detailed resources about troubleshooting bank connections that you may find useful moving forward: