I almost gave up recently thinking that I could not get the nagvis working again. The nagvis installation is quite easy now the trick is to assure that you configure nagios correctly to provide mklivestatus information. Once you achieve this the problem is to say to nagvis to use this information. The problem is that it is almost nowhere documented.
Tip to install mklivestatus: Follow the installation steps specified in
https://exchange.nagios.org/directory/Documentation/MK-Livestatus/details
So here we go if you are certain that mklivestatus works then you need to edit in nagvis the following file :
/usr/local/nagvis/etc/conf.d/demo.ini.php
-> vi /usr/local/nagvis/etc/conf.d/demo.ini.php
Now assure the backendtype is set to mklivestatus
backendtype=mklivestatus
Now your nagvis should start to see your information from your nagios setup.