Cant get star alignment to work

[blinky]

I took 2 sets of data of the Horsehead on 2 different nights, the camera was rotated slightly between sessions.... First night, RGB 5min subs, 2nd night RGB 15min subs.  For some reason Star Alignment wont work.....  I cant throw them all into the batch align tool as I changed the gain of the CCD between the sessions so have 2 different bias frames. Anyway, I have stacked them individually, the 2 different nights and that works. So...... I thought I would grab the calibrated frames from both nights, add them to the Star Alignment tool and off it would go but it wont find any star matches at all....
Here is an example of each of the nights data - a single calibrated sub from each...

http://endor.uv.es/files/data/public/9f1edb.php

[TobiasLindemann]

It looks like only one image is flat-calibrated. You should also debayer the subs before StarAlignment.

[blinky]

Yes I only took flats for the 2nd lot of images but I expect the problem is that I need to debayer the subs before stacking - did not realise that bit!