guage issues

[70nova]

I have been trying to install an autometer speedo to no avail. The cable that is supposed to plug into the back doesnt seem to fit. I think what is happening is the plastic piece that spins the guage isnt going all the way into the guage.... is there a specific way to do this or am i just really this stupid, I have been dicking with this for what seems like forever.

thanks guys