If you run Visual Dialplan on MS Windows OS please add the following lines in vdp.l4j.ini file:

-Dhttp.proxyHost=proxy_host
-Dhttp.proxyPort=proxy_port

Fields proxy_host and proxy_port should be replaced with your settings.

If you run Visual Dialplan on Lilnux OS please add the following line in vdp.sh file:

-Dhttp.proxyHost=proxy_host -Dhttp.proxyPort=proxy_port

And of course, replace proxy_host and proxy_port fields with your settings.