Wordpress website hosted in Plesk does not load CSS content with 403 Permission denied error

Plesk for Linux kb: technical

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Wordpress website hosted in Plesk does not load CSS content.
In the web browser console .js and .css elements failed with:

CONFIG_TEXT: 403 Permission denied error

In /var/www/vhosts/example.com/logs/proxy_error_log:

CONFIG_TEXT: 20585#0: *137 open() "/var/www/vhosts/example.com/httpdocs/wp-includes/js/wp-emoji-release.min.js" failed (13: Permission denied), client: 203.0.113.2, server: example.com, request: "GET /wp-includes/js/wp-emoji-release.min.js?ver=5.4.2 HTTP/2.0", upstream: "https://203.0.113.3:7081/wp-includes/js/wp-emoji-release.min.js?ver=5.4.2", host: "example.com", referrer: "https://example.com/?page_id=22"

Domain misconfiguration.

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Solution 1

Log into Plesk
Enable the option Serve static files directly by nginx in Domains > example.com > Apache & nginx Settings:

Solution 2

Log into Plesk
Change "run PHP as" to "FPM by Apache" in Subscriptions >example.com > PHP settings: