It seems there are 2 adb version in your system. Please find them out and keep the adb in your Android SDK folder only, delete all others folders that including adb file.
You can find out which adb you are using from Application Monitor:
It might be a problem if the adb is not the one in you Android SDK folder.
In my case, I found I was running adb from here:
/Library/Application Support/RSupport/Mobizen2
after deleting the Mobizen2 folder, then all adb commands work fine.