kboudre: Thank you very much for contacting the Intel® NUC communities. We are sorry to hear there is no video when using the external video card.
In order to try to make the video card work with the NUC, we can try a BIOS update to the latest version which is 0052, using the F7 method:
Just to rule out a possible problem with the thunderbolt port, not sure if you have the option, but if you connect a different device on it does it work properly?
For this scenario the issue could be related to compatibility, Intel tested the NUC with different peripherals, as you can see on the link below some of the Thunderbolt docking stations are actually fully compatible with the unit, but we cannot guarantee that all the external video cards will work with the NUC:
In this case, I encourage all the peers viewing this forum, that if you have any comments or suggestions on this subject to post all the details on this thread.
Any further questions, please let me know.