USB TTL cable no longer working

[taros]

My serial cable no longer works. It used to work.

I connect it to the Euler connector,

TX: pin 29
RX: pin 30
GND: pin 34

Then on Linux, 

Code:

cu -l /dev/ttyUSB0 -s 115200

I do not get any response from "cu".
I tried two such cables. Is it possible that the cables got damaged? What can done to deal with this?
Initially I was worried that I bricked the board. However, I managed to boot an image off the microSD card, that had HDMI output.