En los logs se ve el error:
httpd: Syntax error on line 56 of /etc/httpd/conf/httpd.conf: Syntax error on line 7 of /etc/httpd/conf.modules.d/00-proxy.conf: Cannot load modules/mod_proxy_ajp.so into server: /etc/httpd/modules/mod_proxy_ajp.so: undefined symbol: ap_proxy_check_connection
Entrar en SSH y descargar:
wget https://plesk.zendesk.com/hc/article_attachments/9768964964882/psa-mod_proxy.rpm
Ejecutar:
rpm -Uvh psa-mod_proxy.rpm
reiniciar apache: service httpd start
Tambien puede ser por esto: https://support.plesk.com/hc/en-us/articles/12377563593495