Matomo encountered an error: Uncaught Exception: Piwik and/or some plugins have been upgraded to a new version. --> Please run the update process first. See documentation: in /data/websites/ Stack trace: #0 [internal function]: Piwik\Plugins\CoreUpdater\CoreUpdater->dispatch() #1 /data/websites/ call_user_func_array() #2 /data/websites/ Piwik\EventDispatcher->postEvent() #3 /data/websites/ Piwik\Piwik::postEvent() #4 /data/websites/ Piwik\FrontController->init() #5 /data/websites/ WP_Piwik\Request\Php->call() #6 /data/websites/ WP_Piwik\Request\Php- (which lead to: Session must be started before any output has been sent to the browser; output started in /data/websites/