Posting is a co-requisite to merit in order to rank-up. As has been stated often, you should take a look at these threads in depth:

Merit & new rank requirements.
Enhanced newbie restrictions & requirements.

As you’ll see, you need an activity of at least 30 (which you have) and at least one Merit (which you lack). The change you are asking about took place during September 2018, and is described on the second thread I referenced above.