I installed LAMP stack and followed the following tutorials to make my droplet ready I installed Wordpress on main domain and PHP script on subdomain! Wordpress is working well but when i open the subdomain index.php file load well but when i click on Login/Signup Page it gives me "Not Found
The requested URL /app/login was not found on this server." ! Same script works fine on shared hosting and now i want to switch to VPS but encounter this error! I contacted the script developer he said it's due to .htaccess file not working or executed! System is using the default settiings and ignore the .htaccess file placed in subdomain! Please help me :')

Site Url:
alphafire.me
subdomain: alphafire.me/app

Tutorials Followed:
https://www.digitalocean.com/community/tutorials/how-to-set-up-apache-virtual-hosts-on-ubuntu-16-04
https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-phpmyadmin-on-ubuntu-16-04
https://www.digitalocean.com/community/tutorials/how-to-install-wordpress-with-lamp-on-ubuntu-16-04