Website on GCP cant be reached on some wifis

I am using GCP, nginx and domain name from "name.com" to deliever my website. It can be reached on mobile network but doesn't work with wifi.

Although on some wifis you can reach my site with around ~60% (from those i have tests) you cant.

It might have to do something with DNS / DNSSEC but its litearly a guess, I am clueless.