My website is not opened on some computers

I'm using CentOS Web Panel.
I have my 3 domain on Digitaocean server
super-cars.club
iletisim-telefonu.com
contactphone.net

My website is not opened on some computers.
The computer needs to change the DNS address. It opens smoothly on Google DNS (8.8.8..
but example 195.175.39.39 does not open in the metro Ethernet DNS,
Every day I get a warning from the people to the opening of my website.

info:
Digitalocean server, CentOS Web panel installation, use CloudFlare, WordPress script. domains from the isimtescil.
Even before these problems do not remember doing anything to cause it.
Bind ns not start,
Therefore, I am using the CloudFlare.

What can I do?

you should check this with your server admin also dns test would be needed for checking if your dns servers are fine.

http://leafdns.com/