Is the Manager interface enabled in your Asterisk?
Go to your /etc/asterisk/manager.conf, your conf shoud be like this:

[general]
enabled = yes
port = 5038
bindaddr = 0.0.0.0

[your user]
secret=xxxxxxxxxx
deny=0.0.0.0/0.0.0.0
permit=127.0.0.1/255.255.255.0
permit=192.168.1.0/255.255.255.0
read = system,call,log,verbose,command,agent,user
write = system,call,log,verbose,command,agent,user

Remember to set a password (secret) for this user! there is a security issue on Digium (ASA-2007-012).

Once setup the Manager , go into the Voix Manager setting and fill the required field.