Scanner "linking error"

Mercedes » E-Class » 2003-2009
Problem Description

I have a 2007 Mercedes w211 that will not link to either obd2 scanner that we have tried. Both scanners work on other vehicles.  We have tried all of the tips and tricks we have come across.  Yes, the fuse is good, yes the pins are fine, yes there is power to the plug.  Both scanners come, initialize, run through their set up, and then both give a "linking error" and "waiting for communication" messages.  Does anyone have any input at all?  Thanks in advance.