You'll probably need to check the admin page to see what domains are being blocked when you visit the sites and then whitelist those particular domains.
Whitelisting And Blacklisting Is Different On Pi-hole
Whitelisting or blacklisting a site on the Pi-hole works differently than traditional ad-blockers. This is because the Pi-hole works at the DNS level, which should make more sense as you read on.
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Let's say you want to whitelist pi-hole.net. With a normal ad blocker, you would just whitelist that domain. But on the Pi-hole, you need to do a little investigation into the site you want to whitelist. Now pi-hole.ne…