Good. You've got one setup that works and one that doesn't. That's a perfect diagnostic scenario.
Compare all the hardware and settings on the two systems to see what is different. If this process does not lead you to finding the solution on your own, then share your data with us.
As it stands we don't have nearly enough information to go on. I for one know nothing about WMC LiveTV or the hardware involved.
Pay particular attention to what type of audio outputs you are using and what they are connected to. (analog, optical, hdmi etc.) Are you using different sound cards? What audio settings are you using in WMC? Look at anything else that might be related to your sound settings.
Please be more specific when you say
In the living room I try to do the same thing and there is no TTS audio until I escape out of Live TV mode.
Does that mean that the TTS from earlier suddenly gets spoken when you exit out of Live TV? Or just that subsequent TTS actions work?
Normally this is caused by a program having exclusive access to the audio output and not allowing the TTS engine (or any other program) to use it. If you have any settings that allow you to choose Direct Sound instead of WASAPI then choose Direct Sound. If you are using WASAPI or digital-passthrough, then TTS will not work and the only other option is to send TTS to a different audio output (which is what I do).
This concept has been discussed exhaustively on the forum in the context of XBMC/Kodi but the same principles apply.
