Hi, I have requested my PIN on May17th and I didn't received yet. What should I do for the next step?
You requested it? That means that was your second one, right? It's automated once you reach $50. Anyway, if you reached $50, Google will automatically send your PIN. If you haven't received it within 4 weeks, request a new one.
Request a new PIN at the date it is available to be requested again. I requested for my 3rd and last PIN before I actually recieved one.