Genesys Cloud Embeddable SDK microphone mute/unmute not working

Trying to toggle the agent mic from a custom Client App widget but conversationService.mute(true) does nothing. The call state remains ACTIVE and no conversation:participant:modified event fires. The widget has full permissions and the token is valid.

const client = this.client;
await client.conversations.conversationService.mute(conversationId, true);
console.log('Mute triggered');

Checked the network tab, the request completes with 200 OK but the agent is still transmitting audio. What’s the correct method to force a local mute?