This has been answered here: How can I change a LinkedIn app's permissions?
Short answer: You must apply to the Marketing Partner Program.
LinkedIn has made a lot of changed to their API over the past few months. Check out the latest permission changes relevant to this post:
EDIT: Confirmed. I didn't receive a notification that I was approved through the process above, however, it's 30 days later after applying and I just noticed there was a new product available under "Products" once you are logged in and on your App in the developer portal. You have to add the "Marketing Developer Platform" product from there, and once again fill out an application:
Image may be NSFW.
Clik here to view.
After completing the new application, they say they will provide you with confirmation within 90 days.
