Hello, I've been taking a look at this.
First of all, are you checking the capability removeParticipantsCapability before trying to remove a participant from the conversation? You won't be able to remove a participant from a conversation that has already been created. Only if it's on draft.
For conversations that are already created, you can't kick a participant, but a participant can leave the conversation on his own.
Charly - JSCSDK Support Team