Why can't I upgrade Hero's Elite Skills?

What does my Login History show? How do I find friends in Plarium Play? How do I avoid phishing? How do I ensure my account's security? Why is it essential to confirm my email? How do I do it? How do I enable and activate two-factor authentication? How do I log out of my account? What is a Plarium ID? How can I reinstall Plarium Play? My game won't load. How do I fix it? How do I find my Purchase history in Plarium Play? How do I choose the country whose currency will be used for payments? How do I delete my credit card? Why can't I make a payment? How to save game progress by syncing Raid accounts? Where can I find my account ID? Why has my daily reward chain been reset? How can I sync my game progress across my mobile device and Plarium Play? How can I get help for Hustle Castle? What should I do if I can’t download Hustle Castle? How do I upgrade walls and gates?