It appears that your firewall may be blocking Box or you are encountering an error.

Please contact your IT administrator to configure your firewall to recognize all sub-domains of .box.com, .box.net, .boxcloud.com and .boxcdn.net. The ports used on these domains are 80 and 443.
See our Firewall FAQ.

If that does not resolve the issue, then please submit a support ticket at https://app.box.com/help.