It would not hurt to reach out one more time.
If you don't get a response after that or if the response you get back is another brush off, move on.
I don't believe in chasing people around. I will always follow up twice. If I don't hear back, then I move on. No hard feelings. Time is too valuable for me to sit around and wait too long. In general, lack of follow-up is just bad business practice. I would hate to be in the middle of any project and not be able to get important answers...delays will snowball.
How hard is it to at least say "I'm still working on this. I'll circle back as soon as I find out....blah blah blah."? Takes two seconds, but so important because it lets the other parties know that whatever the question/issue is...it has not slipped through the cracks and is being investigated/looked in on. I like accountability.
I practice this all the time in my corporate job too. I email once, email a follow-up. Then I call. Then I will show up in that person's office/desk and talk in person. Nothing confrontational. I do this to everyone....from people on my team to my SVP. Just a "Hey, I know you're busy, but I really need an answer to ABC. Since I'm here, got two minutes?". I sit my butt down while I'm saying that - makes it a lot harder for people to say they're busy at the moment and can't talk.
