Activating Elementor Shows Error

[ehome]

I have tried to both GeneratePress and TwentySeventeen themes, when I tried to activate Elementor plugin, it will show me this error:
Fatal error: Maximum execution time of 30 seconds exceeded in [path]/wp-includes/class-json.php on line 799

I have tried to remove Elementor and reinstalled it, it showed the same thing. What should I do?

 

[3lias]

You might want to rule out if a plugin is interfering with Elementor by de-activating all plugins and trying to activate Elementor alone and see if it's a plugin problem or file problem.

 

[ehome]

I have deactivated all plugins except 'Akismet and Jetpack , even deleted a few of them, it didn't work. Really have no idea what else to do.