It is very important to open all posts before interacting with them - ie. buying/liking or commenting on them.

Only posts that have been opened count as an impression and impressions are what increase your cashable balance.

Tips to encourage opening of posts:

One way to encourage people to open your post is to make the post long enough that you need to open the post to carry on reading ...

Obviously important  is also to make it interesting enough for someone to want to continue reading it  (I battle with this one!)

We need to all open posts and help each other out to create impressions.