Hi mythrilfoundry,
I understand you're having fundamental issues with your online banking connection in QuickBooks Online. Error 103 is commonly an error with your User ID or password for your bank account. Or there could be additional security requirements that you needed to address like one-time passcode or token code in your online banking.
Kindly log in to your online banking website and check if your bank has a message or update that needs your attention.
Once done, let's go back to the Bank transactions tab and do another bank sign-in info in QuickBooks.
- Click on the Transactions tab and click Bank transactions.
- Click on the bank account.
- Click on Edit and choose Edit sign in info.
- Manually enter your bank's User ID and password.
- Click on Save and connect.
Then, check if the error has been removed and new transactions has been downloaded.
In the meantime, you can manually upload your bank transactions using CSV file while waiting for a resolution.
If the issue persists, I recommend contacting our Customer Care Team through Chat or Phone. That way, they can further check your account in a secure form.
Post again in the Community if you have further concerns. I am around to help you.
