To further help you with this, may I know the specific bank you're having problems with? Or have you encountered any error messages when attempting to accept transactions? Any information is a great help so I can find you a timely solution.
In the meantime, let's access your QuickBooks Online (QBO) account using an incognito mode. Private window prevents storing cache and web history to avoid issues when running websites. Below are the shortcut keys you can use: