That should work just fine.
Are you sure everything else in your setup is fine? The event is in your animation? You updated your Spine export? No errors logged?
The default case is also if you're mixing between two animations, the outgoing animation's events don't fire. This behavior can be changed by setting the TrackEntry's EventThreshold value.
0
means events don't fire when mixing out.
0.5f
means events stop firing halfway through the duration of the mix.
1f
means events can fire until the mixing is complete.
That may not be related to your problem but it may be worth checking depending on what you're doing with animations.