How were you powering the TIU when performing the test? Hopefully via a 12V or higher adapter plugged into the TIU aux port.
I just tried it both ways- allowing the TIU to be powered via USB connection from the wifi and then with 12V into the aux in. I then in turn lost the 12V out of the AIU connector when the TIU is only 5V powered, and it returns when I provide proper aux power.