Make sure they are using
http://rcwpcanada.x10.mx/ , NOT
https://rcwpcanada.x10.mx/
They can also get the raw error using telnet. Below is an example. Bold, underlined text is input:
telnet rcwpcanada.x10.mx 80
Trying 198.91.81.4...
Connected to rcwpcanada.x10.mx.
Escape character is '^]'.
GET / HTTP/1.1
host: rcwpcanada.x10.mx
HTTP/1.1 200 OK
Date: Fri, 23 Jun 2017 19:53:27 GMT
Last-Modified: Thu, 22 Jun 2017 15:18:01 GMT
Content-Type: text/html
Vary: Accept-Encoding
X-Varnish: 127566559 129171612
Age: 153
X-Cache: HIT
X-Cache-Hits: 1
Accept-Ranges: bytes
Content-Length: 76006
Connection: keep-alive
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "
http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="
http://www.w3.org/1999/xhtml">
<head>
...
<title>RCWP Home Page</title>
<meta http-equiv="Content-Language" content="English" />