ZenZombie said:

I got 3/3 but cant claim reward. My hero has 3 pieces of atk% at 3* or higher.

Hello!

That looks like a visual bug.

Try to:

• Log out of your account and back in.
  
  
• Reinstall your game.
  
  
• Clear your game cache files.
  
  

If nothing above will work I suggest you to send a support ticket.