G540 and Sherline vfd

Ok I have gotten my g540 all wired up but I can't get my spindle working.. using the 3 vfd pins to replace the potentiometer on the sherline drive. I get no response.. I'm also attempting to use a relay to replace the on/off switch on the drive. Switching the relay with output 1 which I am also not getting a response from...
Has anyone used this combo or have any experience setting up a g540 and vfd?
Thanks..

Kevin
NSR Customs