Give me some more details and I will try to help. What kind of board were you trying to use? What kind of software are you using for psk 31? What radio are you using?
Some things to think about?
If you want to key with VOX, can you adjust the level at which VOX keys the transmitter to make it key at a lower level. and therefore be more reliable?
Can you key your transmitter manually with MOX? Many transmitters can be keyed manually from the front panel. This method works quite well.
Is the software configured to actually key the proper serial port to which the board is connected? Did it ever work?
Will look forward to hearing from you.