OK, since you are using filezilla to do the upload, you will need to be aware of the file locations in relation to each other.
Look at the Files panel in Dreamweaver. you have created a test subfolder and created the form there.
The helper files created by form builder will always be created at the root of the Dreamweaver site. When uploading the files, you need to maintain this relationship.
Upload the form to /test/contact_us.php on
but notice that the webassist folder is at the root of the DW site and not in the test directory. this means when uploading it to the server, you cant upload it inside the test directory, but have to upload it to the root of the site on the host to maintain the file relationship.