Can't connect to any server that uses Cloudflare

For the past few days I haven't been able to connect to just about any website that is behind Cloudflare. This includes their own services like their website and 1.1.1.1 DNS as well as other sites that rely on them, like Discord, 9gag and the Steam store. Pinging them doesn't work at all. Traceroute shows the same issue for all of them, where the connection gets dropped when it leaves Cox's network.

Tracing route to one.one.one.one [1.1.1.1]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  192.168.0.1
  2     8 ms     7 ms     7 ms  10.28.64.1
  3     8 ms     9 ms     9 ms  100.127.74.184
  4    18 ms     8 ms     9 ms  68.1.0.187
  5     *        *        *     Request timed out.
  6     *        *        *     Request timed out.
  7     *        *        *     Request timed out.
  8     *        *        *     Request timed out.
  9     *        *        *     Request timed out.
 10     *        *        *     Request timed out.

This issue only happens when connecting to sites over IPv4, sites that uses IPv6 are unaffected (alas, most sites don't use IPv6). I've occasionally been able to get it to work at random by fiddling with my router settings, but then I'll change something else and it will stop working, even if I change the settings back to what they were.