2080Ti FE in Core X won't work. Or is it the Core X itself?

Hi Friends,
so I buyed an Core X eGPU and plugged my also freshly buyed Geforce RTX 2080Ti Founders Edition in it.
I've installed the 2080Ti drivers, restarted my system (Windows 10). Now I wanted to start the fun. But:

Right when I connect the Core X via Thunderboldt to my Razer Blade* the fans from the Core X + the 2080Ti fans are starting like a Jetplane and won't stop until i unplug the cable or switch the Core X off.
But even worse: Windows just do not regognizes that i plugged in something at all.
Nothing happens besides the intense fan-noise.
There is also no new GPU listed in my hardware manager.
Still only my build in 2070 Q-Max and Intel(R) UHD Graphics 630 listed. Exactly like when i do not have plugged in anything. There is just no sign at all that i plugged something to the system.
But the 2080 for sure can't be supposed to be this loud in normal use. The fans really go crazy here (not in a good way).

Does anyone have an idea? Is it likely a hardware defect? I may have to say i bought it used on Amazon. I often buy stuff 2nd hand on Amazon. Never had problems. And I want to be sure if maybe i did something wrong before blame the guy i bought the card from.


PS: I removed the 2080 to test what would happen. The Core X fan still is on. But only a little bit noisy. Maybe that is normal. So the 2080 is the crazy loud one. Still no sign that i plugged anything at all on the system. No message from Windows or anything. Fair enough this time of cause really nothing is in the Core X ... so maybe thats normal too?

System:
* = Razer Blade 15 Advanced Edition - Full HD 300Hz - GeForce RTX 2070 Super Max-Q - Black
Windows 10
Core X - Black
Geforce 2080Ti FE
Geforce drivers and Synapse 3 are installed.
Did testing to remove and put back in the 2080 already.
Restared the system several times etc

I would love to hear something from you. Did i miss something? I am a bit of hopeless right now ...