I have not bought C-Points in a bit but I run STO through Steam and am given the option to buy C-points with my Steam wallet. I have linked my Cryptic and PW accounts. Like I said I have yet to do so but it looks like I can get around Zen by going through Steam.
I've had nothing but trouble with PW and buying points. I even submitted a ticket and nearly 3 days later I -still- haven't gotten a response. It's making me very angry, wanting to cancel my subscription, and very unwilling to spend ANY money on this game or anything PW related. Which really does make me sad, since I love STO.