call wp_insert_user in custom class doesnt work

In addition to the debugging advice from @s_ha_dum, you could try to catch the possible WP_Error thrown by wp_insert_user():

$user_id = wp_insert_user($params);

if ( is_wp_error( $user_id ) )
{
   echo $user_id->get_error_message();
}
else
{
    printf( 'User created with user_id = %d', $user_id );
}

Maybe the user already exists?

You could also use email_exists() and username_exists() to check.