Windows 8.1 Setup aborded

Hi,
I am really new to NSIS and I have inherited an old NSIS Installer Script from a colleaque.
My problem is I have installed NSIS 3.0 and installed all the necessary plugins for the script.
I have read the forum threads of installing on Windows 8+
I have integrated

ManifestSupportedOS Win7 Win8 Win8.1 {8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}

!define RequestExecutionLevel highest

into the script.
The compilation of the script is successful but when I try to start the script on an Windows 8.1 machine I always get the same error
Setup supports only Windows 2000, XP, Vista and Windows 7. Setup will abort now.

Any idea what I am doing wrong?

Regards
Edmund

!define RequestExecutionLevel highest has no effect unless you are using a 3rd-party header file from the wiki.

Your error message has to be coming from something in your script, NSIS will never display that string.

Verify that example1.nsi works and then go back to your script and try to find the cause...

Thank you, that was the hint I needed.
I have extended the Section where the windows version was checked and now it is running without any error message.

Regards
Edmund