I have found the solution and wanted to update it here in case others step on it. Besides of clearing your browser's cache and history, Turbotax itself actually keeps the linked account credentials somehow.
The following solve the issue. This is for online version.
On the left menu, under Document, you should see a Documents and a Linked Accounts tab. Click on the Linked Accounts tab, and you should see all the linked accounts that have been setup to import. Click on the "..." corresponding to the account that was linked, and simply remove it. That's it. Turbotax will ask you for a new account/credentials next time when you want to import data from the same financial institution.
