Stopped quite a few years ago yeah, apparently due to a falling out between the various different train companies . Massive shame.
Sadly even that looked difficult for us in March, the Zagreb - Sarajevo leg had something like a 100km gap in the route between the final Croatian station and the first Bosnian one. 12 hour train would’ve certainly been preferable to 7 by taxi…
Definitely worth doing Mostar by train if you can next time, for the view of the mountains alone!