Tektronix and Keithley

Hello,
I have a 2701 DMM + 7709 switch model and I want to measure e resistance from backplane panel.
I use a 2-wire ohm function and I get a OVRFLW. If I measure it from the front panel it works.
What can be the problem? Thank you for your advises!

In addition to closing the appropriate channel on the 7709 card, also be sure to press the Inputs Front/Rear switch on the front of the 2701. It needs to be pressed in for Rear to route the cards to the internal DMM.

Thanks for your replay.
I change it to the REAR on front from the beginning but it not helps, also i tried to use a system channel operation and a multiple channel operation it still not working.
If you know what more can cause that problem I will appreciate your help!