What can I say, software can be tough... But are not gonna give up!
Let's try next
Quit the VOX app (COMMAND+Q). It's important!
Run this two commands in terminal :
launchctl remove com.coppertino.VOXCloud
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
Open ~/Library/Containers/ in finder (You can press Command+G and paste it there) remove folder com.coppertino.VOXCloud and empty trash.
Run this last command in terminal:
killall -SIGTERM cfprefsd
Open VOX and try to sign into LOOP.
Looking forward to your reply!