[halbritt]

It's very likely that they have 1.1.1.1 in their "bogons" list and have for a very long time.

Bogons are a list of prefixes that most ISPs blackhole as there is usually never any legitimate traffic bound for those destinations. RFC1918 addresses, for example.

I can't reach 1.1.1.1 either, but 1.0.0.1 works fine. Maybe try that.

[plb4333]

Could it be that 1.1.1.1 is blocked because it uses a secure protocol as opposed to 1.0.0.1 which is unsecure. This would be for the sake of monitoring traffic.