I experienced exactly the same issue there, the device was also not showing any lights on the device. I also there did the 'Allowed apps downloaded from.' Black Magic, so that should be ok. Just to further test the adapter thing, I got my hands on a Macbook Air (11inch mid 2012) also running High Sierra 10.13.3, this with a firewire port buildt in so no need for the adapter. I remember testing the Recorder earlier and I have seen the lights on the device lighting up on my last tests, however for this test it is now not lighting up any more. This only appeared once and after I allowed it it did not appear again after I uninstalled and reinstalled the drivers. I have 'Allowed apps downloaded from.' Black Magic in the section of the Security & Privacy in settings. With my Macbook Pro 2017 model I am using a certified USB-C to thunderbolt adapeter from apple (_/uk/shop/product/MMEL2ZM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter) in case you where wondering, so it should be completely functionable apple product to get thunderbolt working on this newest version of the macbook pro. Hi there thanks for the comments, I have made some more testing.

Black magic desktop video dartfish