It looks as though you are using some code that you have to follow instructions for which you have not quite followed correctly.
The following code at line 28:
<!-- List of required fields, seperated by a comma-->
<!-- If you do not wish to require any fields, leave value="" -->
<input type="hidden" name="require" value="Senders_Name,email ">
You need to change the last line shown here to read
<input type="hidden" name="require" value="Senders_Name,email,Message,Requirements"
If I were you I would also change the name= and value= all to lower case too although not necessary it is good practice and will .
Try this first if it will not work then let us know again !