Just checking in here - did you ever reach a solution @swift3r ? Running into the exact same issue as well. Migrated project to creator companion standards, my parameter driver interface looks just like yours w/ base & avatar SDKs at version 3.1.11
The parameter driver is hit in play mode when the controller transitions to the state that hosts it, but the driver never… actually sets the parameter, in this case to a random value b/w 1-4.
Short of starting from scratch in a whole new project I’m kindof at a loss - I configured the transition out of the state w/ the parameter driver to have an exit time & transition duration of 0.0001 just in case that might help too but no luck.
Rather puzzling as to why it’s not working, ahaha. Nothing in the documentation or elsewhere I’ve been able to find on it of course - this post is the sole mention of this particular problem.