2018/08/04 16:02:23 [error] 530#530: *9 FastCGI sent in stderr: "PHP message: PHP Warning: Invalid argument supplied for foreach() in /var/www/html/prestashop/classes/shop/Shop.php on line 347" while reading response header from $upstream, client: 192.168.0.180, server: _, request: "GET /prestashop/ HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.0-fpm.sock:", host: "192.168.0.175"
2018/08/04 16:03:37 [error] 530#530: *9 FastCGI sent in stderr: "PHP message: PHP Warning: file_put_contents(/var/www/html/prestashop/var/cache/prod/cacert.pem): failed to open stream: No such file or directory in prestashop/classes/Tools.php on line 1948" while reading response header from upstream, client: 192.168.0.180, server: _, request: "GET /prestashop/install/index.php?restart=true HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.0-$
2018/08/04 16:09:40 [error] 532#532: *79 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 192.168.0.180, server: _, request: "GET /prestashop/install/index.php?installDatabase=true&_=15$
Установочный скрипт прибивается по таймауту. Смотри настройки в php.ini. Конфиг nginx не вижу, поэтому предположу, что копать в сторону /etc/php/7.0/fpm, /etc/php5/fpm или cgi рядом.
