I have a Dell TB15 connected to two 1920x1080 screens (one via display port, other via HDMI; DP chaining always made trouble) and been using it with an XPS13 9360 running Ubuntu, and a Dell mobile workstation running Windows 7. Some firmare and driver updates needed but then it worked like a charm.
Now I have a MBP... A1708 Mid 2017 running MacOS X 10.13.6, and it does not work at all. When I plug in the TB15 on one of the two TB3 ports the LED on the plug stays off. But the funny thing: the Mac gets charged from the TB15 dock via thunderbolt. So I guess it must be a firmware / driver issue.
What I have tried:
checking if the two TB ports on the mac make a difference. no.
installing all OS updates offered. no.
checking if the dock gets shown in System information -> thunderbolt (see screenshot). "No device connected" on both ports.
installing the Thunderbolt3Unblocker kernel module that allows for using hardware unsupported by Apple from  see also . A...
kextstat | grep ryan
... in the console after a reboot shows it, so I assume it is loaded. I did expect too much, as I read that it only unblocks devices that show up in system information with a remark "unsupported"; but worth a try. However, nothing.
- resetted SMC, NVRAM; see . On reboot after command-option-p-r it asked me for a wifi key during boot, did something then booted up. But also did not solve the problem.
Now I am stuck. I really do not want to buy another dock as the setup has been working for me well; but I have to get the mac to work in my environment...
Any ideas appreciated.