Device Discovery Problem

I have a group of Connect ME -S devices that cannot be detected by Digi device discovery. I am using the developement kit connected to a router to try to discover. I have 20 parts, 11 of them worked fine the other 9 cannot be discovered. The set-up is the same for the parts that I can get work and for the ones I can’t. The parts all have the same revision. I have tried downloading the lastest version of the device discovery tool with no change. On the modules that can’t be discovered the router fullduplex/collision LED stays yellow, for the units that work this LED goes out after the ME reboots. Any suggestions of how to get around this problem?
The parts are marked PN:(1P)50000878-01 L 95010624 C