1. When plugin activated on WP network and some blogs have wrong/empty Piwik options (wp-piwik-site_id etc) - it's continuously requesting Matomo server via WP_Piwik::requestPiwikSiteId() trying to update site_id, but blog option saved via self::$settings->setOption ( 'site_id', $siteId ); is overridden then from $this->settings in Settings::save()
   Also, in TrackingCode::__construct() it calls self::$wpPiwik->updateTrackingCode () with empty $siteId and $blogId params
   Suggested fix: use get_current_blog_id() when $blogID is empty and remove else and always store local blog options in $this->settings, maybe limited by condition like

	public function setOption($key, $value, $blogID = null) {
		if (empty( $blogID )) {
			$blogID = get_current_blog_id();
		}
		$this->settingsChanged = true;
		if ($this->checkNetworkActivation ()) {
			update_blog_option ( $blogID, 'wp-piwik-'.$key, $value );
		}
		if ($blogID == get_current_blog_id()) {
			$this->settings [$key] = $value;
		}
	}

to avoid any collisions..
2. Replace add_blog_option() with update_blog_option() to update existing options
3. Same for add_site_option() vs update_site_option() in Settings::prepareTrackingCode()
4. Fix PHPDoc param order