Input 3 domains are fine. One is only visible via proxy. What can cause this?

[ScottAMains]

Hi folks. I've just been working on a new build and noticed an issue that I can't see any obvious problem.

On my install I have 4 sites, 3 of which resolve fine. The fourth only loads up when viewing through a proxy. Nothing was done differently during the domain setup process.
nameservers and all DNS records look pretty fine thanks to Igor on a previous thread.

ping & nslookup all give back the right data that it exists where it should exist.

Issue: when viewing either by my smartphone/tablet or laptop I keep getting err_name_not_resolved however, the above ping and data is fine, and when checking through isitdown it says that its fine, and even using screen-shot (website screenshot) it shows the landing WP install I have happening. This has happened on both my regular internet as well as using mobile hotspot.

IPAddress banning and ModSecurity have been temporarily disabled to see if those were responsible, however it seems like it is not.

Is there something that I am missing that could be causing this issue?
Many thanks

 

[ScottAMains]

I think I may have answered this myself. Attached screenshot for anyone in the future that may experience this. My mobile phone operator is doing a thing whereas everyone else can access it.