Nadeaux

Anyone ever run into problems with the OBDII readers not being able to connect. My wife's 2006 R350 has had the check engine light going on and off for the past 2 days but my reader is unable to connect. I have an actron cp9135 which i've had for many years with out a problem but it won't read the benz code. Is this common and any other ways to get the codes read? Still have some time on my CPO warranty so worst case i'll just take it to the stealership.

Thanks for the help.