Well, I was able to connect a GTX460 from the stoneage, so I assume it is neither the cable and connectors, nor the PSU. I looked at the pins of course, they did not look suspicious.
The gfx board was in surprisngoly tip-top shape, almost no dust, after 10 months of use. The sharp edges of the ventilators had a little bit, and the plain upside surface which is cobered with that cosmetic, colour-lit fancy lightshow thing (switched off), but the spaces between the slats: when I send pressured air thorugh it, no dust came out, and before they looked absolutely clear.
The tower and the way they arranged the components and cables seem to provide very excellent airflow inside the tower. The air filters in the walls in front of the coolers, and at the bottom, no matter how primitive they look, seem to do some real good job there. I clean them once a week (easy access). The air outlets on all sides also showed no dust.
My old system was a dust trap and was heavily covered with dust after 5-6 months. The clean shape of this tower came as a real surprise to me. After ten months of use! It looked as if used for just a week.
I fired a mail to their tech department. I assume the gpu card gets send in and checked. I run via my Linux notebook right now, and yesterday evening had a very nice and long playing session with my almost forgotten PS4: Gran Turismo, The Hunter Call of the Wild, and Wipeout for dinner. I enjoyed it, and so am relaxed. I had almost forgotten that I have a small collection of 4 or 5 really good games for that thing.
I got it in a sale right for an opportunity like this: for times when my main rig would break down.
Man, do I sound like an addict, or what...