After switching a website to FPM served by nginx in Plesk, it fails to load with “404 Not Found” on all pages except start page

Log in to Plesk and add the content below to the Additional nginx directives field of the WordPress domain at Domains > example.com > Apache & nginx Settings:

if (!-e $request_filename) {
set $test P;
}
if ($uri !~ ^/(plesk-stat|webstat|webstat-ssl|ftpstat|anon_ftpstat|awstats-icon|external-nginx-static-location)) {
set $test "${test}C";
}
if ($test = PC) {
rewrite ^/(.*)$ /index.php?$1;
}

• • If this is a WordPress installation, which is located in a subdirectory (for example, “httpdocs/sub-dir”) or this is a WordPress multisite network based on subdirectories, add the /sub-dir/ before /index.php?$1 so it will look like this:

    rewrite ^/(.*)$ /sub-dir/index.php?$1;

    Note: For WordPress multisite network based on subfolder, add the above rule for each subdirectory.

1. Log in to Plesk.

2. If you are in Power User view, switch to Service Provider view at Tools & Settings > Interface Management.

3. Add the rewrite rules below to the Additional nginx directives field at Service Plans > service_plan > Web Server tab:

   if (!-e $request_filename) {
   set $test P;
   }
   if ($uri !~ ^/(plesk-stat|webstat|webstat-ssl|ftpstat|anon_ftpstat|awstats-icon|external-nginx-static-location)) {
   set $test "${test}C";
   }
   if ($test = PC) {
   rewrite ^/(.*)$ /index.php?$1;
   }

4. Click Update & Sync to apply the changes.

1. Connect to the Plesk server via SSH.

2. Create a directory for custom templates and copy default configuration templates there:

   # mkdir -p /usr/local/psa/admin/conf/templates/custom/domain

   # cp /usr/local/psa/admin/conf/templates/default/domain/nginxDomainVirtualHost.php /usr/local/psa/admin/conf/templates/custom/domain/nginxDomainVirtualHost.php

   Note: Any changes made in original configuration templates will be lost after an installation of Plesk micro-updates.

3. Open the file /usr/local/psa/admin/conf/templates/custom/domain/nginxDomainVirtualHost.php in any text editor (for example, with the “vi” text editor) and replace the section:

   • on Plesk Onyx 17.5, 17.8:

     <?php if ($VAR->domain->physicalHosting->directoryIndex): ?>
     location ~ /$ {
     index <?=$VAR->quote($VAR->domain->physicalHosting->directoryIndex)?>;
     }
     <?php endif ?>

   • on Plesk Obsidian:

     <?php if ($VAR->domain->physicalHosting->directoryIndex && !$VAR->domain->physicalHosting->proxySettings['nginxProxyMode']): ?>
     location ~ /$ {
     index <?=$VAR->quote($VAR->domain->physicalHosting->directoryIndex)?>;
     }
     <?php endif ?>

   with the following content:

   location ~ / {
   index index.php index.cgi…