Can't get sounds working

Hello, I feel like I've tried everything, but no matter what I do I can't get sounds working with MythicMobs. I'm running the following versions:

Spigot version 1.10.2
MythicMobs version 2.5.0
Also most recent version of ProtocolLib

I've tried various permutations of the syntax for sound, for example
- sound{s=entity.endermen.scream} @Self
- effect:sound{s=entity.endermen.scream} @Self
- sound{s=entity.endermen.scream} @target
- sound{s=entity.endermen.scream}...

Can't get sounds working