Cannot save template on page editor

[wpplumber]

I had the template save operation working before while using an OOP architecture but when I moved the plugin code to this WP boilerplate I got the following message error!

Is it something with permission? I used the following route for backoffice page.

$router
	->register_route_of_type( ROUTE_TYPE::ADMIN)//ADMIN_WITH_POSSIBLE_AJAX )
	->with_controller( 'Admin_Settings@register_hook_callbacks' ) 
	->with_model( 'Admin_Settings' ) 
	->with_view( 'Admin_Settings' );