Check whether xastir is compiled to use festival.
Click on help menu (to right of interface menu) & select 'About' option.
This will show what options are compiled in.
I think the first xastir in Raspbian repo was compiled without festival support.
I had to compile from source to get it to work.
Just recompiled from source & mine stopped working too!
From memory, when configuring I had to do
To compile I did
The j4 flag uses 4 threads (on Pi2) to shorten compile time.
My problem might be that the festival server isn't running at boot time.
I posted some instructions a while back when I first ran into problems,
So I need to look at them myself. (Found your old post while searching!)
And while I think about it, Xastir *always* starts without new Callsign announcement (in case you are receiving internet APRS traffic)