Sounds like you are not getting a signal to the speedometer, thats what that usually means.
Try re-setting the sensitivity from low to high
double-check the wiring, make sure you have the speedo signal input going to the right wire (tan/white I believe)
make sure the speedometer gear drive is in the tranny, had a customer a while ago tht was missing the drive grar, took a while to figure it out
Any questions, feel free to ask!
Mark