One is only visible via proxy.

Hey, guys. I was just working on a new build and noticed an issue where I don't see any obvious issues.
On my installation, I have 3 sites, 2 of which resolve normally. The fourth one is loaded only when viewed through a proxy server. Nothing was done differently during the domain setup process.
the name servers and all DNS records look pretty good thanks to Igor in the previous thread.
Problem: When browsing on my smartphone/tablet or laptop, I keep getting err_name_not_resolved, however, the above ping and data are OK, and when checking if everything is ok, it says everything is OK, and even when using a screenshot of the screen, it shows that the target WP installation should happen. This happened both on my regular internet and using a mobile hotspot.
IP address ban and ModSecurity security have been temporarily disabled to check if they are responsible, however, it seems that this is not the case.
Is there anything I'm missing that could cause this problem?

There are a number of reasons why a DNS domain name resolution might fail. One of the more common reasons is that the DNS server is (temporarily) unavailable. In this situation, if there are no entries for the website you are trying to access in your browser cache or in your operating system's DNS cache, the DNS will not be able to resolve the domain name. The previously mentioned address entries can themselves also be a possible cause for the “ERR_NAME_NOT_RESOLVED” error in Chrome. For example, this error can occur if the browser tries to answer a DNS query using a cached address when the IP address has since been changed. source: http://proxies.com