Last time I checked, the "transfer" options were "from share" to "penfed accounts". I do not see an option to transfer money to external checking account (I do have linked checking account from different bank and this account does not appear when I chose "transfer from share").
When you setup an external transfer, you get the option of transfers in or transfers in/out.
I just started the process of settting up an in/out transfer, they're going to deposit small amounts in my external checking and I have to confirm the amounts. Then I can ACH out.
I imagine when you set up the account you reference you only set up the transfers in option. Reset it up and you should be fine.