In order to activate a credit card in MineralTree, it must first be set up as a credit card account in QuickBooks Desktop.
Navigate to Lists > Chart of Accounts
From the bottom righthand corner, press Account and select New
Select the Credit Card account type
Fill in an Account Name, and an Account Number (Acct. No)
It is not necessary for the Credit Card Acct No to be the actual credit card number; you can select any account number that will fit in with your Chart of Accounts structure.
Please note: Subaccounts must have the same type as accounts, so a Credit Card account cannot be the subaccount of a Bank account.