Your server is missing a couple of things.

If you have any difficulty installing Pancake, don't forget:
We can install Pancake for you, for free.
Just start a free support ticket.

Please fix the below errors and refresh to re-check.

Status Requirement
Pancake must be able to reliably detect whether URL rewriting is on or off.
Your server must be able to communicate with pancakeapp.com (otherwise you won't be able to receive updates).
Your license key is valid. Your license key is not valid.
The Curl PHP extension must be installed.
The GD PHP extension must be installed.
The JSON PHP extension must be installed.
The DOM PHP extension must be installed.
The MySQL (or MySQLi) PHP extension must be installed.
The XML PHP extension must be installed.
Your server must be able to make TLS 1.2 connections to other servers.
'; ?> The system/pancake/config folder must be writable.
The uploads directory must be writable.