1747 scanner comm light always red flashing,help

What i am using:
Rack 1:
1,slc500 cpu 5/03 slot 0
2, 1747-sn scanner ser:b slot 1
3:16 pionts ac input slot 02
4:16 points ac input slot 3
5:16 points ac output slot 4
rack 2:
1, 1747-asb adapter ser:a slot 0
2,16 points ac output slot 1
3,16 points ac output slot 2

distance between two racks:6 ft

scanner setup:
Sw1:1 on, 2 on
scaned input words:32
scaned output words:32
interrupt service routine:0
m0 length:3300
m1 length:3300
g file length:3

g file configration:
Logical rack 0---group 0---1/2 rack

adapter din setting:
Sw1: 1-8 on,
sw2:1-7 on, 8 off
sw3:1 off,2-5 on,6 off,7-8 on


pc connceted to cpu,remote run,no fault

stadus:
Scanner comm light: Red flashing fault light: No light

asb light:comm light: Green flashing fault light: No light
display:ade

reading from program : M1:1.0/0=1

how to active scanner?

Anybody could help to find out where is the issue?
Thanks!

Did you try swapping the Remote I/O signal wires at one end ?

Hi,Ken. Thanks for replying.
I have tried ,if I switch the wires,no communication any more.
I am sure the comm cable connection is right.
Also,I have tried to switch another rack,another cpu (5/04),another sn card and asb card.nothing changed.