PROBLEM All pages show the same content

[dynazor]

Hi!
I'm running the latest 3.3.10 GS on XAMPP,
I'm starting a project - a blog website, making the template from scratch.
There seems to be a problem that I cannot solve -
the <?php get_page_content(); ?> (which I put in template.php) outputs only the home page,
so does the html title and page title...

It happens either with or without fancy URLs, plugins, original themes, etc...


What should I look for?

Thanks in advance

Info:
GS 3.3.10
XAMPP 3.2.2
Running Apache with all needed components on and installed

Edit 1-
Debug mode findings:
using custom navigation plugin;
Undefined variable currentpage in plugins\custom_navigation.php on line 73

When disabling custom navigation and putting normal getnav;
Undefined variable: currentpage in admin\inc\theme_functions.php on line 583

Edit 2-
Reinstalling GS and putting in the theme;
From installation:
GetSimple 3.3.10 - Latest version installed
PHP Version 5.6.23 - OK
Folder Permissions OK - Writable
cURL Module Installed - OK
GD Library Installed - OK
ZipArchive Installed - OK
SimpleXML Module Installed - OK
Apache web server Apache/2.4.17 (Win32) OpenSSL/1.0.2d PHP/5.6.23 - OK
Apache Mod Rewrite Installed - OK

Now it's Working, fixing theme and applying plugins, will report soon back!
(Please don't lock thread, I might run into more trouble.. I don't want to spam the forums)