I'll help you fix the error, tarang.
When you're getting an error 378, it means that QuickBooks is unable to access your bank account using the financial institution's login information.
You'll want to authorized the connection between QuickBooks and the bank by following these steps:
- In QuickBooks, go to Banking or Transactions.
- Click on the account displaying Error 378 and select the link that says Sign in to [Bank Name].
- Enter your login credentials and choose all of the accounts you want QuickBooks to have access to.
- Click Continue (this word might vary slightly depending on the financial institution). The “OAuth” window will close after this step.
- Hit the Update button to download the transactions.
I'm also adding this article for more information: What to do if you see a bank error or bank transactions won’t download.
Please keep me posted if you have additional questions about QuickBooks Online Banking. I'll be here to help you again.