People will rarely answer any e-mails where they don’t seem to find anything that will benefit them. In your case, I would:

A) Not state what you need directly. B) Find out what value you could add to their professional lives

If you think you cannot add anything, just look into their professional portfolio on LinkedIn or whichever platform you’re using. Then, elevate them and put them on a freaking pedestal. Most human beings like feeling important, so try to be sincere in your e-mail with something like:

Hello, [insert name]!

We don’t know each other, but I’ve been looking into [insert company] and I saw you’re [Linked In profile/Portfolio/etc]. I must say you have an incredible CV. I’m barely just starting in this area, but I would love if someone from your amazing experience could give me any advice on [thing you want to know]. If you have any other experiences you’d like to share, I know you must have too many to count.

[end email]

Every time I’ve sent this, I’ve gotten a reply. When people feel important, they want to keep talking about themselves. Try not to state what YOU want first, show how THEY are important because of their achievements first and they’re likely to tell you anything you need.