Hi I've simple differential configuration amplifier with ref powered from 1/2VCC VCC is 3.3V. Differential signal is output from AMC1200. When I tried to power it up I have nothing on output.
When you say you have nothing on the output, do you mean that the output is at 0V?
If you haven't tried yet, please disconnect the AD8236 from the AMC1200. Tie both inputs, as well as REF, to Vcc/2. You should read the same (1.65V) at the output.
Separately, with the setup connected, could you probe the inputs of the AD8236 to see what's going into the device?