This was before, but now all Google Play developers can reply to user reviews.
check this article:
All Google Play Developers Can Now Reply to User Reviews
In order to reply on reviews, please follow these steps posted Here in Developer console help center:
Sign in to your Google Play Developer Console.
Select an app.
On the left menu, click Ratings & ...
This feature is currently only available to select developers, not all. I also do not have this ability.
From Developer Console Help:
We are also piloting a new developer response feature, where select
developers can publicly reply to any comment once. In such a case, an
email will be sent to the commenting user with an option to update the