10 days ago, I received an e-mail on a Friday from a potential employer offering me a Skype interview for a position I applied for. They said directly, "I'd like to speak with you this coming week," and asked for my availability. After giving them my availability, I didn't hear back. I sent an e-mail the Tuesday after (3 days later) to "check in" and gave my availability again. Still nothing. Should I send ANOTHER follow up e-mail? Would it be acceptable for me to call? Or should I just wait?
Interesting situation. It's incredibly unprofessional of them to leave you hanging like that, and it should serve as a red flag for you.
That being said, in order to remove all doubt, you should simply call them and get an answer. I wouldn't hold my breath however. Sadly, chances are that their behavior is due to having found a candidate they prefer over you.
You are trying to wring blood from a turnip. I suggest you leave them and concentrate on your next prospect.
Remember, when searching for a job, the only time you stop pursuing companies is when you have a written offer in front of you that you are willing to sign. The reason is what you're experiencing now: one company pauses (forgets, cancels) the process, and you sit waiting. If they end up getting back to you with a, "sorry, we already filled that position," then how much time have you wasted? Could you have put that time to better use instead?
Forget these guys and get to work on your next company. Smart companies know that good people don't stay unemployed long, so when they find one, they don't waste time messing around.
I recommend giving them a call. From being on the recruiting side throughout my whole career, I have seen many reasons that could explain your experience. (Not necessarily acceptable professional reasons, but reasons, nonetheless). As a Recruiter, I would have given a candidate a chance to explain even if they were a no-call-no-show to an interview, because you never know what might have happened. I see this as the same type of situation.
A Recruiter could be out sick for a week, and despite having backups, etc., some things slip through the cracks.
I've seen Recruiters so incredibly busy that they keep thinking it's "next on their list" and keep unintentionally pushing off setting up your next step.
They could just be waiting on the hiring manager's confirmation, which they expect to get any second. And, for whatever reason, the hiring manager isn't getting back to them, so the Recruiter didn't mean to delay 10 days - they kept thinking any-minute-now they'd have their follow up for you.
Those are some devil's-advocate possibilities. However, I hope that offers some perspective on what could be occurring on the other side.