The Synch Accounts utility will synchronize accounts that have been added but are missing in the Account Selector.  Follow the solution on How to Synch Accounts.

If the account is still missing from the Selector after Synching Accounts, edit the account in the Chart of Accounts grid, change the description for example, and this should rewrite the record.  You might need to exit Fundware and log back in, to see if the account is refreshed and then pulls into the Account Selector.