Updating an Existing Property on Workflow vote

I don´t see any "apply" in your code. You set the Property, but only to the temporary context. You don´t seem to use edit/apply to actually save your new value. 

And I see a second problem. As far as I understand you want to update your history value:

You use this line to get the value:

string history = controlledItem.getProperty("_conversation_history","");

But that line to update the value:

this.setProperty("_conversation_history",newconvo);

In your context "this" represents the "Activity" item while controlledItem represent your change process. 
I am not sure if controlledItem.setProperty in combination with edit/apply would work, cause the controlled item is something generated by the helper function. But you can give it a try. 

If it doesn´t work, get the id of the controlledItem and do a direct edit of the Change process.

I don´t see any "apply" in your code. You set the Property, but only to the temporary context. You don´t seem to use edit/apply to actually save your new value. 

And I see a second problem. As far as I understand you want to update your history value:

You use this line to get the value:

string history = controlledItem.getProperty("_conversation_history","");

But that line to update the value:

this.setProperty("_conversation_history",newconvo);

In your context "this" represents the "Activity" item while controlledItem represent your change process. 
I am not sure if controlledItem.setProperty in combination with edit/apply would work, cause the controlled item is something generated by the helper function. But you can give it a try. 

If it doesn´t work, get the id of the controlledItem and do a direct edit of the Change process.

Thank you very much! Below is the code that ended up working.

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;

string idofitem = controlledItem.getID();
Item item2 = inn.getItemById("smc_TechInquiry",idofitem);
item2.setProperty("_conversation_history",newconvo);
item2.setProperty("_reply_to_requestor","");
item2.setProperty("_message_from_requestor","");

item2.setAction("edit");
item2.apply();

return this;