Lets encrypt ip6 problem

I am having a problem with Lets Encrypt on one of my servers. It will not verify, yet the verification url works fine in browser. I have determined that it works with ip4 but curl shows that it fails with ip6 it gives a 404 Not Found error.
The url is
http://s-vcch.net/.well-known/acme-challenge/sYxqCykjoZo5SFJ7YqmcYjKIuf70EcVAzNh8-1RYEH8
how do I fix this?

The only way I have found to fix this for now is to remove the IP6 from the DNS records, not the best way but it will have to do for now.