Cannot find the new columns I added to a list a week ago

Hi, I'm using VS2012.

I added a couple of new columns to an existing list over a week ago.  Using C# code, I was able to connect to the site and got the list.  Able to update the columns until I got to the new column4,  and then I got exception error.  How to fix this?  Thank you.

exp = {"Column 'new-column4' does not exist. It may have been deleted by another user.  /Lists/MyList"}

           ClientContext context = new ClientContext("https://xxx.yyy.zzz");
            List MyList = context.Web.Lists.GetByTitle("MyList");

            ListItemCreationInformation itemCreateInfo = new ListItemCreationInformation();
            ListItem newItem = MyList.AddItem(itemCreateInfo);
            newItem["column1"] = column1Value;
            newItem["column2"] = column2Value;
            newItem["column3"] = column3Value;
            newItem["new-column4"] = column4Value;
            newItem["new-column5"] = column5Value;
            newItem["column6"] = column6Value;

Thank you