https://reddit.com appears to be blocked when using mobile data, but works on my home wifi connection. A previous poster with this problem fixed it by disabling parental controls, but these were already disabled on my account.
If I try pinging reddit.com I get:
64 bytes from lang-sspiprxy.network.virginmedia.net (81.99.162.48): icmp_seq=1 ttl=247 time=79.5 ms
I checked various other sites that would definitely be blocked by parental controls (porn, gambling, etc.) and they're not working either, so it looks like parental controls have been enabled for my account, even though when I check settings, they're off.