Data Form plugin in insert mode doesn't work

I wanted to implement the Data Form plugin to add new rows to my table. I have configured the plugin, both the Plugin Config and the Form HTML. I marked the plugin as a Table plugin and it shows the button on the front-end table. But when I click this button, I get the following error:
 
As you can see on this picture, this error also occurs on the JCTables demo site, on the Web Tickets demo.
Please provide a solution.

Hi Hessel,

Please allow us a day or 2 to follow up on this, the demo site is one or 2 versions behind, so it might be out of sync with the latest version of JCTables.
We see the edit works, but not the insert.

I am assuming you have the latest version of JCTables.

In the meantime, herewith some points to make sure are in place on your side (sample below is plugin configured to edit), and button set for row display

Data Form WikiDocs

Plugin : "Data Form"
Plugin Config : {

   "tableName" : "jctickets",
   "indexField" : "id",
   "formAction" : "edit"

}

Form Html :

<table style="margin: 10px;">

  <tr>
    <td>Date:</td>
    <td><input class="easyui-datetimebox" name="date_time" style="width:200px" data-options="required:true"></td>
  </tr>

  <tr>
        <td>Subject</td>
        <td><input class="easyui-textbox" name="subject" style="width:100%;" data-options="required:true"></td>
  </tr>

    <tr>
    <td>Category</td>
    <td>
       <select class="easyui-combobox" name="supportcategory_id" style="width:100%;">
          <option value="1">Clock Enquiry</option>
          <option value="2">General Enquiry</option>
          <option value="3">Payroll Enquiry</option>
          <option value="4">Techincal Support</option>
       </select>
    </td>  
    
  </tr>
 
  <tr>
    <td>Progress</td>
    <td>       <select class="easyui-combobox" name="progress" style="width:100%;">
                    <option value="requested">Requested</option>
                    <option value="completed">Completed</option>
                    <option value="inprogress">In Progress</option>
                    <option value="closed">Closed</option>
       </select>
        </td>
  </tr>  
 

  <tr>
    <td>Priority</td>
    <td><select class="easyui-combobox" name="priority" style="width:100%;">
          <option value="none">None</option>
          <option value="low">Low</option>
          <option value="medium">Medium</option>
          <option value="high">High</option>
       </select>
        </td>
  </tr>    

  <tr>
        <td>Description</td>
        <td><input class="easyui-textbox" name="description" multiline="true" style="width:100%; height:200px;"></td>
  </tr>

</table>