Check your "hosts" file, maybe it is directing network somewhere wrong:
https://www.heise.de/tipps-tricks/Ho...n-4928321.html
Or try to change the DNS used to some other, not the one your ISP provides.
Alternative examples are descriebd here at the antivirus side of Avast for example:
https://support.avast.com/de-de/arti...ubleshoot-DNS/
Can be "maybe" changed at your Router too, instead at your local network connection (lan or wlan adapter settings).