Why PLC5/40E program don't allow me to force I/O?

I have a PLC5/40 program upload from client site. and I download to another PLC5/40E. The Force I/O selection is gray color which don't allow me to force I/O, How to fix this probleum?

From the help

"Set bit S:26/6 if you must restrict forcing or data table changes when the processor keyswitch is in RUN mode. When (0) the data table and forces can be edited in RUN mode; when (1) the data table and forces cannot be edited when the processor keyswitch is in RUN mode."

S:26/6 is already "0", but it still can be force I/O.

There are four class 1,2,3,4. all are set to allow to force in the program.

Where are you seeing the grey-out.
There are a few ways to force inputs and outputs. One way is to right click on the output or input you want to force then click on force on or force-off. Another way is to go to the data table and select force, then enter a 1 or zero then enable the force. Remember to disable all forces when done.

Thank you Mickey, I am so careless.

Your welcome. I have some screen shots if needed.
I'll post anyway

Woops, I missed the simple answer.

wilsonzhu I would suggest reading up on forcing in AB PLC's, there are some things to watch out for that can be quite dangerous. For example, if you leave your force in there and then disable forces, the next guy can come along and put in a different force, enable the forces and then whatever you had forced will come on or off too.

The first thing to look for when forcing something is to make sure there aren't any forces in the program already. This has been discussed before here.