it will say codeplug too new for application if your cps is outdated. you might even get "unsupported model" because of earlier version 6.04 cps. i think the "Couldn't open port." is a hardware problem. just for kicks clean around the connection between the radio and cable and make sure all the pins on the cable are clean and straight same for the receiving end
I agree with chrismol1. "Couldn't open port" is definitely a communications error. I wouldn't run and get a software upgrade until you are sure you need it. If there was an issue with the CPS version, you would get a different error message. What does the device manager say your "true" serial port is on? Changing the parameters in device manager doesn't do a thing, CPS runs its own speed directly.
I would be thinking bad cable, poor contacts. Are you running your RIB on battery? Try a fresh one. I had a real M battery only RIB that was so-so. Dumped the 9 volt and cobbled a 8 cell AA holder to it for 12 volt in.
Ran great, didn't have any more probs, and it lasted a hella long time.
To be considered, a radio will (rarely) have a fubar serial line and just refuse to be read or written to. A trip to depot (ouch) will take care of that.