I appreciate you joining us here in the Community space. I can share some information about connecting your bank with QBO.
I've tried searching BMO Harris Bank N.A. - Retail, SB in QuickBooks and it's showing the www3.harrisbank.com website. Since this is still the old one, you can request the URL's update by calling our phone support agents.
They have the tools to create an escalation ticket and to communicate with your bank to process your request. Check out this link to get their contact details: