Thunderbolt bridge 'inactive' on MBA 2014

Hi

I'm trying to use my daughter's 2014 MBA and need to get ethernet connected via an Apple Thunderbolt Bridge.

The machine just does not see the device. The Sys Info says 'no device connected'. Network in the Sys Prefs shows that Thunderbolt is 'inactive'.

I've reset PRAM and SMC. I know that the ethernet cable is working (unplugged it from my iMac where I don't use WiFi).

I'm at my wits end now ... looking for helpful suggestions on how to resolve this problem.