National Instruments Software Engineer web Based interview questions

First round was just phone call to understand your background and your interest. A couple days later, I got an email for next round and asked my SkypeId, number, and availabilities. I got confused and asked them if they would do Skype or number call, but provided all my info to them. A couple days later, they sent an email they will cancel the interview without any reason. I asked them any reasons politely, but never got email anymore. VERY unprofessional