For PHP7 and above, the pid file would be placed in /run/php, which hasn't been created on filesystem. Thus NGINX can't work with PHP-FPM.
templates/etc/php/fpm/php-fpm.conf.j2
20:pid = {{ php__run_base }}/php{{ php__version }}-fpm.pid
env/tasks/main.yml
76: php__run_base: '{{ "/run/php"
77- if (php__version | version_compare("7.0", ">="))
78- else "/run" }}'
For PHP7 and above, the pid file would be placed in
/run/php, which hasn't been created on filesystem. Thus NGINX can't work with PHP-FPM.