I want to ensure that you're able to change the bank account for invoice payments, @jules-thefoxagen.
When updating the bank account, make sure to login as company admin to your QuickBooks Online account on a web browser. Once done, follow the steps below:
Click on Settings ⚙, then choose Account and settings.
Hit the Payments tab. In the Deposits section next to Standard Deposits, choose Change bank.
Choose Add new bank account.
Fill in the routing number and account number of the bank account you want to change to.
Click on Save.
Check the bank account info and make sure it’s selected before completing your request.
If the issue persists, I suggest logging in to your QBO company using an incognito window to check if you're experiencing any browser-related issues. Here are the shortcut keys to open incognito: