With regards to IPv4 resolution failing:
This is basically a "best effort" thing on our part. It requires that your network topology is dual stack, and it works by having you send a request to us over a A-type DNS record that only gives an IPv4 address (ipv4.kagi.com
). This is a common trick that similar "what is my IP" websites that give you your IPv4 also use.
If your network does not provide an IPv4 gateway, then there is simply no way we'll be able to get it (you don't have one), and I'm not aware of any way we could possibly inform you of the reason.
If you can find another IP check site that gives you an IPv4 address (please check Kagi again at the same time in case your network changed), then we can take a look at how they do it.
As for the text mismatch... don't know about that one, it is a simple string check that does not fail with the example given; please report if you see that again.
So, until we can verify that it is actually possible for us to give you an IPv4, will mark this as Clarification needed for now.