wp_login action hook not working

I have developed a plugin which works fine, except I need to have some code to execute when the user just logs in, and it does not work.
Here is the code in my plugin:

add_action('wp_login', 'kpcms_update_XAPI_Actor_on_login');
function kpcms_update_XAPI_Actor_on_login() {
	ChromePhp::log('login');
	session_start();
	kpcms_setXAPIActor();
}

ChromePhp::log('login'); is for a Chrome extension which allows to print directly to the browser console.
Nothing is printed, and the function kpcms_setXAPIActor(); is not executed.
Can't see what is wrong here.
Thanks in advance for feedback.