Ah yes, definitely this as well OP. It’s just so rare for this to be the case that I didn’t consider it. It’s rather odd for DNS to not work only on select sites like that. Hopefully your ISP isn’t deliberately DNS spoofing / DNS poisoning, but that’s one method that many countries governments and ISPs use to block users from using sites they don’t like.
Fun Fact: There was even once an issue with DNS poisoning from China was beginning to spread to the rest of the world because DNS servers learn from each other and there were so many DNS servers in China like this.
Try testing by changing your DNS to one of many public DNS servers. Not suggesting any of these as a permanent DNS replacement (you need to be choosier about that one, preferably one that’s trusted and supports DNSCrypt), but just to check:
Google: Public DNS | Google for Developers
Primary: 8.8.8.8
Secondary: 8.8.4.4
Verisign: Verisign is a global provider of domain name registry services and internet infrastructure - Verisign
Primary: 64.6.64.6
Secondary: 64.6.65.6
OpenDNS: Setup Guide | OpenDNS
Primary: 208.67.222.222
Secondary: 208.67.220.220
Level3:
Primary: 209.244.0.3
Secondary: 209.244.0.4
DNS.WATCH: https://dns.watch/index
Primary: 84.200.69.80
Secondary: 84.200.70.40
Comodo: Free Comodo Secure DNS | Best DNS Security Solution
Primary: 8.26.56.26
Secondary: 8.20.247.20
Dyn: Internet Guide Setup Dyn Help Center
Primary: 216.146.35.35
Secondary: 216.146.36.36
Private Internet Access: PIA Support Portal (under “DNS Leak Protection”)
Primary: 209.222.18.222
Secondary: 209.222.18.218
More: https://www.lifewire.com/free-and-public-dns-servers-2626062
OpenNIC Public Servers: https://servers.opennic.org/
If none of those work, it’s something else.
It’s always best to use your VPN’s DNS though. I mean, I assume you trust your VPN handler if you’re buying their service. Using a different DNS than your VPN’s means you now have to trust two companies as opposed to just one.
I always use my VPNs but on the very rare time something seems wonky with them, I use Veracrypt’s.