Error 103 typically means invalid credentials or a timeout during authentication with the bank. Since you've mentioned that you entered the correct credentials. Visit your bank’s website, check if it requires third-party access, If so, follow your bank’s instructions to turn it on.
Then, enter your bank sign-in info in QuickBooks.
Follow these steps to connect your bank account to QuickBooks. Make sure to select the same bank you signed in to earlier. Some banks have very similar names.