[kohlschuetter]

Disconnected as in "network"? What PCIe card do you use? Can you update the firmware (maybe from Windows)?

Also check the BIOS settings (try setting TB security to "No Security" or "User Authorization")

Some OEM Mellanox cards can be cross-flashed to NVIDIA's stock firmware, maybe that's also relevant.

[madduci]

It's embedded in the laptop (a HP ZBook from work). Disconnected as in network. Laptop charges, but signal doesn't work. With Thunderbolt 3 devices, it works. (The card itself is T4).