I recently changed my ISP from Optus to TPG and when I tried to start my local apache instance and I got this error
httpd: apr_sockaddr_info_get() failed for 192-168-1-107.tpgi.com.au
httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName
That gave me a hint that my local hostname had changed. I reset it back to what it was originally like this:
sudo hostname myoldhostname.local
Restarted apache and it was smooth sailing again.