Trading is not an unlimited event in , as players can only trade so many times before they have to get more energy to do so.This is represented by the Trading Hourglass, which looks a lot like the other two hourglasses in the game except this time it's green.
Unfortunately, the mechanic is similar as well, meaning that you will have to restock some of this energy if you want to keep trading.
Trading in is a new mechanic and one that players have been hoping for. Unfortunately, it comes with some of the same problems other mechanics in the game have, which is mainly that it may require real-world money and a lot of patience.
However, in this case, the challenge is simply finding a Trade Hourglass to use. Trade Hourglasses are primarily available as mission rewards.
Right now, there is not a clear way to get them as a reward or purchase them, but that is rumored to change once the new set goes live along with a new event in .