For all you guys that are still not working AFTER installin NGINX addon.
Installation of NGINX objective is to keep ssl interface with HA from outside your LAN while you keep plain http from inside.
So, after installing the addon you need also to configure your config yaml to get the internal communications without ssl encryption and change the base url of the tts from the external address to the internal one (http://192.168.0.X:8123)
So yours must look like this:
Hope it helps!