Please follow the below template, it will help us to help you!
I am trying to set up pi-hole on a computer running ubuntu 14.04 lts, and whenever I try to run the command pihole enable it says "Restarting DNS forwarder and DHCP server configuration syntax check ...fail!"
Expected Behaviour:
The pihole should start blocking ads when I try to use it as the DNS server
That said, if you would like to try an older version of pi-hole, you can change to version 3.2.1, which may well work on your system. (I have personally tested downgrading from the current Pi-hole to version 3.2.1 on ubuntu 14.04.5 by this method, and it is working at this time).
If you have not already, please ensure that your system software up to date. Either by the Software Updater, or from the commandline:
sudo apt update && sudo apt upgrade
After rebooting, the instructions to change the version of pi-hole are here
(Also note the additional instructions from 2018-02-07 at the bottom of the first post - edit the file /etc/dnsmasq.d/01-pihole.conf as directed before you follow the main instructions).