Originally Posted by hurnik

I'd say Yes. On the Farelock purchase screen you're presented with two button options (not checkboxes, buttons, so they are mutually exclusive). One for credit card/payment types. The other for Electronic Certificate. (Note the word Certificate vs. Credit). If you choose the Certificate option, you are then prompted for the 10-digit certificate # and a PIN. The FTC has neither. So you'll have to call in.

Note too, that there's no guarantee that the agent can/will convert your FTC to an ETC to then use it. Worst case, they say "no" and you HUCA.