Hangouts Chat Bot "The caller does not have permission", PERMISSION_DENIED

Question

I created a chat bot using the JAVA Api, based on the sample code from the documentation, the Bot uses a service account.

The Bot works fine in one Room, but when I try to use it with a new Room I am experiencing an error.

After adding the Bot to the new Room and trying to post a message I receive { "code" : 403, "errors" : [ { "domain" : "global", "message" : "The caller does not have permission", "reason" : "forbidden" } ], "message" : "The caller does not have permission", "status" : "PERMISSION_DENIED" }

Is there any additional step necessary after adding the Bot to a room before posting messages ?

Any help with this problem would be greatly appreciated!

Code used:

HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport(); 
JsonFactory jsonFactory = new JacksonFactory(); 
HangoutsChat.Builder builder = new HangoutsChat.Builder(httpTransport, jsonFactory, credentials); 
builder.setApplicationName(bot); 
HangoutsChat service = builder.build();

ListSpacesResponse response = service.spaces().list().execute();
// Look for space Space _space = null; 
while (response.getSpaces() != null && _space == null) {    
  for(Space s : response.getSpaces()) {          
    if(s.getDisplayName().equals(space)) {          
      _space = s;       
    }   
  }     
  if (_space == null && response.getNextPageToken() != null && !response.getNextPageToken().isEmpty()) {        
    String pageToken = response.getNextPageToken();         
    response = service.spaces().list().setPageToken(pageToken).execute();   
  } else {      
    break;  
  } 
}

if(_space != null) {    
  Message m = new Message();    
  byte[] data = {0x0A};     
  m.setText(text.replace("\\r", "").replace("\\n", new String(data)));  
  Message r = service.spaces().messages().create(_space.getName(), m).setThreadKey(thread).execute();   
  Element el = new Element("message");  
  el.setAttribute("space", r.getSpace().getDisplayName());  
  el.setAttribute("text", r.getText());     
  el.setAttribute("thread", r.getThread().getName());   
  outNode.addContent(el);  
} else {    
  throw new Exception("SendHangouts failed " + "Space " + space + " not found"); 
}