Just got my new connection and not able to connect to major serves

Pubg - not connecting to server
ubisoft uplay - not connecting to server
Battlefield 4 - not connecting to server
csgo - working
steam - working
browser - working

I tried with my mobile data its connecting. But in Bsnl FTTH its not connecting saying serve busy or not able to connect.

What should I do.....
I am using same router, which I used with BSNl broadband and I tried putting it on DMZ and all but not working

I have this issue where battle.net launcher won't load videos and news, destiny 2 won't login, steam website would not load with public DNS so I have to use bsnl dns or cloudfare dns.

I have BSNL DNS, i tired google and open dns but no change. Did u find any solution

[Solved] Found out there is an option called MTU by lowering the value I was able to access the " not connectable sites and servers"

Wtha was the value of MTU before and after you changed ?