Invalid command ‘ProxyPreserveHost’, perhaps misspelled or defined by a module not included in the server configuration

sudo a2enmod proxy

[Sun Feb 26 03:48:38.613627 2017] [proxy:warn] [pid 9117] [client 94.63.XXX.XXX:49486] AH01144: No protocol handler was valid for the URL /. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.

sudo a2enmod proxy_http

Restart apache and everything should be okay now.
HOORAY!