Sorry to say, but most likely an assembly problem is at the cause of troubles.
Hereby the diagram and PCB layout, to allow troubleshooting. http://www.velleman.eu/images/tmp/mk124.jpg http://www.velleman.eu/images/tmp/http://www.velleman.eu/images/tmp/mk124.jpg
Sorry, this forum does not allow picture uploads
If you can provide LINKS (e.g. by using a free online picture base) to HI-RES and SHARP pics of your assembly (both solder- and component side)
then we can take a look and provide some feedback.
Should you be unable to solve the problem, then you can return the kit for inspection/repair.