Di2 TT shifter not recognised

fredrikb81

One of my Ultegra Di2 TT shifters all of a sudden went completely dead. When I try to configure the system in E Tube, i get the "unit not supported" message as long as it is conneted and nothing works. As soon as I disconnect it, the system works fine and configuration is possible in E Tube.

Any ideas what can be the problem and how to go about fixing it? It just went dead during an indoor trainer right, and I thought these things were supposed to be reliable...