From my understanding, I think Kynu.net may block access outside of Vietnam because it works fine here (I'm in Saigon now), I just accessed it today. It's been good so far, if you guys need any recommendations on which girl is pretty and gives good service for a good price, inbox me.
I'm in Thailand now, and I can access Kynu.net good
When I was in Vietnam, there were a handful of times I was unable to access Kynu.net and it had to do with the some of the Internet providers when using free WiFi at the local cafes. At the same time, I would try accessing from my mobile Viettel 4G and I could access Kynu.net good.
If you are unable to access Kynu.net outside of Vietnam, I would recommend using a VPN. And as others have stated, the first time you access the site, it will require you to wait 5 seconds before loading.