Board Thread:Love Live! School Idol Festival Lounge/@comment-35593064-20180515120754/@comment-29855003-20180516055130

Have you tried contacting their support? I've only tried transferring in JP tho (the one before SIF ID existed) and I had no problems with that.

But for now, try using those coupons/make a new transfer passcode then try again. If it doesn't work, contact their support.