Website PHP files are downloaded instead of executing in a server with Plesk

Symptoms

• PHP is not being handled correctly. When trying to access a PHP page on a website, instead of executing it, it asks to download it.
• The issue appears in case PHP set as FPM application served by Apache.

Cause

Plesk psa-phpfpm-configurator package is outdated.

Resolution

Upgrade psa-phpfpm-configurator package using Plesk installer, following instructions from the KB article: How to install Plesk updates