You need to target a Player (there is an option for that), It doesn't work if you only click on the player.
I will check so I can confirm that actually.
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7. How do I use the abilities?
To use an Ability first make sure you are in OverWatch, by selecting “Play OverWatch “ on the side bar or the “OverWatch” option that appears when you select a Friend as they drive around the Map.
Then, select and target a Friend so that a red crosshair appears over their icon and tap an Ability to deploy it. A few moments later, you will be notified if the Ability was successful or not and will be awarded OverWatch Speedpoints.
Abilities go into recharge each time you use them giving Friends a chance to recover if you use them to hinder them. However, there is no reason why you can’t use a different Ability while another recharges.
