502 gateway ruim por causa do índice indefinido?

No meu site, recebo um gateway ruim 502 após implementar a seguinte configuração:

# Default server configuration
  2 #
  3  server {
  4         listen 80;
  5         listen [::]:80;
  6         server_name microurb.club;
  7         return 301 http://www.microurb.club;
  8  }
  9
 10  server {
 11         listen 80;
 12         listen [::]:80;
 13
 14   # SSL configuration
 15   #
 16   # listen 443 ssl default_server;
 17   # listen [::]:443 ssl default_server;
 18   #
 19   # include snippets/snakeoil.conf;
 20
 21   root /var/www/microurb.com/public_html;
 22
 23   # Add index.php to the list if you are using PHP
 24  index index.php index.html index.htm index.nginx-debian.htm;
 25
 26  server_name  www.microurb.club;
 27 ·
 28  include global/restrictions.conf;
 29  include global/wordpress.conf;
 30 ·
 31 # location / {
 32 #   # First attempt to serve request as file, then
 33 #   # as directory, then fall back to displaying a 404.
 34 #   try_files $uri $uri/ =404;
 35 # }
 36
 37   location ~ \.php$ {
 38     include snippets/fastcgi-php.conf;
 39     fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;
 40   }
 41
 42   # Allow access to the ACME Challenge directory
 43       location ~ /\.well-known\/acme-challenge {
 44         allow all;
 45   }
 46
 47   include custom_config_files/x_protection.conf;
 48 }
 49
 50 server {

 51         listen 443 ssl http2;
 52         listen [::]:443 ssl http2;
 53         server_name microurb.club;
 54         return 301 https://www.microurb.club;
 55         include ssl/ssl_general.conf;
 56         include ssl/ssl_microurb.com.conf;
 57 }
 58
 59 server {
 60         listen 443 ssl http2;
 61         listen [::]:443 ssl http2;
 62         server_name www.microurb.club;
 63
 64         include ssl/ssl_general.conf;
 65         include ssl/ssl_microurb.com.conf;
 66
 67         root /var/www/microurb.com/public_html;
 68
 69         # Add index.php to the list if you are using PHP
 70         index index.html index.php;
 71
 72         location ~ \.php$ {
 73           include snippets/fastcgi-php.conf;
 74           fastcgi_pass unix:/var/run/php7.0-fpm.sock;
 75         }
 76
 77         include custom_config_files/x_protection.conf;
 78 }
 79

Eu fiz um:

sudo tail -30 /var/log/nginx/error.log

E recebi os seguintes erros, mas não sei o que significam:

PHP message: PHP Notice:  Undefined index: success in /var/www/microurb.com/public_html/index.php on line 295" while reading upstream, client: 24.55.9.54, server: www.microurb.club, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.0-fpm.sock:", host: "www.microurb.club"
2018/12/25 20:07:05 [crit] 18408#18408: *40 connect() to unix:/var/run/php7.0-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 24.55.9.54, server: www.microurb.club, request: "GET / HTTP/2.0", upstream: "fastcgi://unix:/var/run/php7.0-fpm.sock:", host: "www.microurb.club"
2018/12/25 20:07:06 [error] 18408#18408: *40 open() "/var/www/microurb.com/public_html/favicon.ico" failed (2: No such file or directory), client: 24.55.9.54, server: www.microurb.club, request: "GET /favicon.ico HTTP/2.0", host: "www.microurb.club", referrer: "https://www.microurb.club/"
2018/12/25 20:07:10 [crit] 18408#18408: *40 connect() to unix:/var/run/php7.0-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 24.55.9.54, server: www.microurb.club, request: "GET / HTTP/2.0", upstream: "fastcgi://unix:/var/run/php7.0-fpm.sock:", host: "www.microurb.club"
2018/12/25 20:07:20 [crit] 18408#18408: *40 connect() to unix:/var/run/php7.0-fpm.sock failed (2: No such file or directory) while connecting to upstream, client: 24.55.9.54, server: www.microurb.club, request: "GET / HTTP/2.0", upstream: "fastcgi://unix:/var/run/php7.0-fpm.sock:", host: "www.microurb.club"

Acredito que o problema tenha raiz na minha configuração acima, mas não tenho certeza de onde. Quando tento descomentar este bloco:

 31 # location / {
 32 #   # First attempt to serve request as file, then
 33 #   # as directory, then fall back to displaying a 404.
 34 #   try_files $uri $uri/ =404;
 35 # }

Recebo um erro depois de executar sudo nginx -tdizendo que tenho nginx: [emerg] duplicate location "/" in /etc/nginx/sites-enabled/microurb.com:31, mas só tenho um. Não tenho certeza por que recebo esse erro.