When using the G/L Account Mass Add/Delete tool,  the appropriate Fund Class(es) also have to be assigned to the GL account in the Master Chart before FIMS can auto build the GL accounts for the funds in those classes.  

If the tool is not creating an account for a fund or group of funds, check to be sure the fund's class codes are in the master chart on that account's line.

If you only want to add the account to one Fund, it is best to add the account manually from the General Ledger Accounts/Account tab by clicking the New button.