Problem with RS232 port

How can i see if my RS232 port/gate is broken at the profilux II unit.

When i should connect with my RS232 cabel it came up no connection to COM1
but in my PC its says that the port Com1 works fine with no problem.

When i scan after com ports it says
No Device is Connected at all COM-ports

Some clue what the problem can bee

these conditions are important:
- our ProfiLuxSER cable is used (not another one!)
- baudrate in ProfiLuxControl and in the device are matching

we had never a ProfiLux with damaged RS232 interface until today - it is not very likely