Unable to install Magento: Unable to install the app because its installation requirements are not met

Symptoms

Magento installation via Domains > example.com > Applications > Magento fails with the following error in Plesk UI:

PLESK_ERROR: Error: Unable to install the app because its installation requirements are not met. Contact your hosting provider to resolve this problem
Requirements
PHP extension
The 'mcrypt' extension was not found.
PHP extension
The 'soap' extension was not found.
PHP extension
The 'zip' extension was not found.

Cause

PHP requirements for the Magento are not met.

Resolution

Adjust the PHP requirements for the application of the domain:

1. Log into Plesk 

2. Go to Domains > example.com > PHP settings switch PHP version to 7.0 and click Apply button.

3. Go to Tools & Settings > PHP settings > select the PHP version based on the one from step 2.
   Make sure that the extensions mentioned in the error are selected:
   - mcrypt
   - soap
   - zip

   

   Note: In case the mcrypt is missing, it can be manually installed using the following article: How to install the php-mcrypt module on a Plesk server

4. Install Magento application again in Domains > example.com > Applications.

Note: Magento 2.1 supports only PHP 7.0. In case PHP 7.0 is not installed, install it according to this KB guide.