Welcome friend, to the new Apple.
I had this problem too, with Nano's that worked perfectly until I installed El Capitan. I worked quite a while before I found out that Apple has implemented a new protective scheme in El Capitan called System Integrity Protection. SIP doesn't let third-party software tickle the system parameters unless it has been approved by Apple. The USB drivers used by a lot of non-native (I'm trying to be politically correct here) Uno variants aren't on Apple's happy-list, and from my investigation, I don't think there's a workaround.
I rolled myself back to Yosemite. If you made a backup before the upgrade, just jettison EC and go back. I can't advise you on how to get rid of EC if you don't have a backup.
Good luck. My opinion of Apple has gone way down.