Sorry to get back so late. I wanted to convey, much to my chagrin, I was using the wrong IP. Plugging in the correct static IP took care of my issue.
With respect to changing IP addresses, I found it to be very easy. I changed my /etc/network/interfaces config file and the balance of the associated network config files updated without a fuss with ONE exception; the /etc/apache2/vhosts/Vhosts_ispconfig.conf required updating with the new static IP for existing websites. New sites created with ISPConfig used the static IP after I changed the server IP in ISPConfig (Management --> Server --> Settings) as well as the existing sites.
Thanks for your help and I sincerely apologize for my error of using the wrong IP to begin with.