The first error:
HTTP Error 405 - The HTTP verb used to access this page is not allowed.
means that the server is configured to reject form posts.
when you submit the UE Form, it sending a form Post to the server, the server is responding to the POST verb and saying it is not allowed. you will need to contact the host to have the server configured to allow the POST form method.
the second message:
HTTP Error 404 - File or directory not found.
is saying that the redirect goes to a page that does not exist on the server.