Answer
I. Enable HTTP methods in IIS:
Connect to the Plesk server via RDP.
Launch Internet Information Service (IIS) Manager at Windows Start > All Programs > Windows Administrative Tools.
In IIS Manager, expand SERVERNAME > Sites > click on example.com > Handler Mappings (under IIS).
Find the handler which is used by the website and double-click on it.
For example, if this is a PHP website, double-click on PHP-php.
Click Request Restrictions....
Switch to the Verbs tab.
Add required verbs in to the verbs field, for example: