"all the sites you mentioned works on my machine. I think there is something strange happening with your network connection."
As I said in my post, they work on mine too - except with the Avast browser. Therefore it's not network, it's browser.
"Try the same website which does not work in other browser at the same time"
I said in my first post I did this. Did you even read or just cut and paste a form?
"- disable Anti-Tracking feature in Secure browser"
Already tried, plus force https (which i think is the problem) and adblock - said this already.
"- disable All AV shields (Avast tray icon menu -> Avast shields control) and restart the browser
- open cmd and type "ipconfig /flushdns"
- if disabling AV shields helped, try to focus on Real Site and Web Shield. It can be one of them. .. or Firewall but I do not think so
- launch Wi-Fi inspector in Avast. Any problems found?"
These would manifest the problem in other browsers - it's not network - it's browser.
"Let me know your OS version, AV version, browser version"
Windows 10 Pro Verson 1709
Avast Program Version: 18.4.2338
Avast Virus definition version: 180602-8
Avast Browser Version: 65.2.491.182
So I'm just done with Avast.
As I originally thought, I think the problem has to do with your setting in privacy-center to force https. This defaulted on and I had the problem. I tried toggling it off and closing and reopening the browser - didn't work. I tried restoring default settings and closing browser and rebooting - didn't work. I toggled force https off again and played with some other stuff, then had to reboot computer for unrelated reason. After rebooting again, with force https setting coincidentally off, it seemed to solve the problem. This is interesting that turning off force https and closing and reopening browser didn't work, but that doing so and rebooting entirely did. I'm very curious how that could be.
Regardless, here are my many problems with Avast:
1/ Your force https toggle sucks. It's a good idea, but it doesn't work. It just stopped some sites from loading.
2/ I've never liked your over frequent churning away at my hard drive with random background task.
3/ I loathed your background downloading/installing/updating stuff without my approval. I know you think this automation is "convenient" for many customers, but it often drags my CPU&HD when I'm doing other work, instead of postponing till I'm done.
4/ I don't need another crap chromium browser anyway. What's the point of a thousand identical browsers named different things taking over the market? How is that secure? Also, google is evil. And mostly, how many years and they can't/won't fix their tab problem. You get to 20-ish tabs and they become unreadable instead of fixed size scrollable right and left. It's maddening. I'm trying Pale Moon (which is Goanna). If I have to try another chromium, it will be Brave next.
Adios.