Multiple Citi credit card account updates

I have 3 different credit card accounts with Citibank. All 3 cards are accessed using the same user identity and password. I am having a continual problem trying to get Quicken to download transactions and balances for the 3 separate accounts in Quicken. I am told repeatedly that the login information I have entered is incorrect yet I am 1000% sure it is not entered incorrectly. Something in the Quicken configuration is obviously wrong and is not being altered when I give it the correct information. How can I correct this messy and irritating situation without losing all the existing data I have on file for these three accounts?