Thank you guys!
@gtsuport, I found out these days that after changing the configuration of any port, Com or Peripheral, I have to turn off the cpu. I will try to do it these days.
@IO_Rack, I tried to upload the program to the PC using that cable but I wasn't able to go online. I used Direct Online option and I got a communication error. With other 2 CJ1M I was able to go online using the same cable and the same method, which make me think that the Com port has died.
I will keep you informed!