Puppet master certificate generation not working
First, try setting dns_alt_names in /etc/puppet/puppet.conf:

[main]
    dns_alt_names = www.puppetmaster.com
[master]
    autosign = true


Then see if your puppet-agent -t run works properly. be sure that you have properly set your server on the puppet client in /etc/puppet/puppet.conf too:

[agent]
    server = www.puppetmaster.com