Knowing the exact issue is important.
systemctl status apache2.service
sudo nano /var/log/apache2/error.log
netstat -ltp | grep :80 # To know if a program is occupying port 80
FYI: Apache modules reside in the following. Sometimes we have a mismatch of modules especially after switching PHP version. If the loaded version is different and the available version is different, that causes an error too.
Mac OS Specific Local Development Environment Issues
#1 Mac OSX apache not starting
# source: https://apple.stackexchange.com/questions/79299/apache-on-osx-10-8-not-starting
sudo apachectl -T
#2 Apache not working suddenly
A lot of things were tried not sure what worked.
This might have done the trick.
# Not sure what did the trick. Try in the following order:
brew reinstall apr-util
brew reinstall httpd
sudo rm -rf /Library/Developer/CommandLineTools
sudo xcode-select --install
# check node