[chirp_users] Error message Arcshell r5

Hi I have been trying to program some new frequencies into Arcshell r5 from 10.13 Sierra and am having some issues with error messages when I select download from radio.I am no techie .See no step by step directions on how to do this.was triumphant that I got my Mac to accept apps from anywhere. So if you have some advice I could use it. I downloaded python and chirp I get error message when I select download from radio.Have RT cable.The salesman said it was compatible with Mac.Do you know?Thank you help would be appreciated.