The answer is to install the php xml package:
sudo apt-get install php-xml <br/>
sudo service php7.0-fpm restart <br/>
sudo service nginx restart
I discovered the actual problem one of the log files:
2017/10/16 22:14:07 [error] 14850#14850: *1090 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Error: Call to undefined function simplexml_load_string() in ...
Turns out that function is supplied by php-xml