You might have come across the following error in your cPanel error log :
SoftException in Application.cpp:267: File “/home/username/public_html/foldername/index.php” is writeable by group
The issue is due to folder and files permission not properly set and cPanel not allowing them to run on the user end.
To fix this issue, simply login into the server (we need SSH access to resolve this) and run the following 2 commands :
cd /home/username/public_html
Replace username by your user.
find foldername -type d -exec chmod 755 {} \; find foldername -type f -exec chmod 644 {} \;
Replace the folder name by your project folder or if your files are in the root directory of public_html then use public_html folder name.