You can try adding an account from another bank (155)

It's a pleasure to have you here, @Ganesh Baliga. Let me provide some information about this error message that you receive when trying to connect your bank with QuickBooks.

Bank error 155 means that your Financial Institution (FI) isn't allowing QuickBooks to connect and recover your data. In case you get this prompt, it means that we're working with your FI to resolve this issue.

That being said, I suggest contacting your bank and request to allow the connection. If the problem persists, ask your bank representative to escalate the case through our OFX Connectivity page for resolution. Make sure to make a note of your case or ticket number for future reference.

As an alternative, you'll want to manually upload your bank transactions into QuickBooks Online. 

Here's how:

1. Sign in to your bank or credit card's website.
2. Follow your bank's instructions on how to download CSV files of your transactions to your computer. 
3. In QuickBooks Online, go to the Banking menu.
4. Click Upload transactions.
5. Choose Browse and then select the file you downloaded from your bank and then click Next.
6. In the QuickBooks account ▼  dropdown, choose the account then select Next.
7. Follow the onscreen steps to match the columns on the file then choose Next
8. Choose the transactions you would like to import, choose Next and click Yes.
9. Once ready, select Let's go.

For more information, please see this article: Manually upload transactions into QuickBooks Online.

Once your transactions are in QuickBooks, it's time to match and categorise them. Afterward, you can reconcile them to ensures your books are accurate. 

Feel free to get back to this thread if you have other banking concerns with QuickBooks. I'll be more than happy to help. Have a pleasant day.