Thanks for bringing this concern to my attention, @Scorcho.
I'm here to help share some information on how you can get past the banking error 103 that you received so you can get back to business.
Banking error 103 means that your banking credentials in QuickBooks Online don’t match what your Financial Institution has on file. If you have an existing connection and you recently changed your banking credentials on your bank's website, be sure to enter your username and password directly instead of allowing the browser to auto-fill your login credentials.
From the left menu, select Banking, and choose Banking.
Locate the card for the account that generated Error 103.
Select the pencil icon.
Select Edit sign-in info.
Enter your new credentials and select Update.
If this is a new bank connection with QuickBooks Online, make sure to select the right bank and enter your banking credentials correctly.
However, if the issue persists after trying these steps, I'd recommend reaching out to our Customer Care Team. They have additional tools like the remote viewing session that can help verify what's causing the issue.
These resources should get you back on track.
Keep me posted how it goes by leaving a reply below. I'll be around if you need further assistance with banking errors or any QuickBooks related things. Wishing you well.