Updating a property on a vote with a server side method.

I am trying to update a property after a user votes on the item in the workflow.

I have this as a Post Method on the workflow server side C#. The variables seem correct, but the property is not updating. 

What am I missing? Thank you for your help!

Innovator inn = this.getInnovator();
Item controlledItem = this.apply("GetControlledItem");
if (controlledItem.isError()) {
return inn.newError("smc_TechInquiry_Notifications: Retrive Workflow: Unexpected error: " + controlledItem.getErrorString());
}


// get the message from requestor and reply to requestor

string messagefrom = controlledItem.getProperty("_message_from_requestor", "");
string replyTo = controlledItem.getProperty("_reply_to_requestor", "");
string history = controlledItem.getProperty("_conversation_history","");

string newconvo = history + " " + messagefrom + " " + replyTo;


controlledItem.setProperty("_conversation_history",newconvo);


return this;

Sincerely,

Conner Davis