Hello, 

Connecting credit cards with sub-accounts can be tricky and you'll need to do a little investigating before you decide the best method.  I highly recommend that you search You Tube for a vide by Hector Garcia called "QuickBooks Online Tutorial: Connect a Credit Card with multiple sub-accounts & How to reconcile it".  He explains it better than I could. 

As far as reconnecting an existing account, you'll need to disconnect the account from the bank feed before it can be available to reconnect.  Otherwise, if you don't do that step first, it will create a brand new account that will have to be merged.  

   1. Look in the existing bank register to find the date of the last synced transaction.  You'll need to enter that date when you reestablish the connection. 

   2. Go to the Chart of Accounts, find the bank or credit card and edit it.  Check the box that says "Disconnect this account on save" and then click Save.  That will free up the account to be reconnected. 

Now you can go back to the Bank Feed and reconnect.  You will get a pop-up asking you which account to link and you should see the one that you just disconnected.  Then it will ask you the date you want to start the sync and you'll want to put in the date that you looked for in Step 1. 

Hope this helps!

---------------------
Dena Martin - Advanced Certified QuickBooks ProAdvisor
Smooth Sailing Business Solutions LLC
Blue Ridge, GA