Hello,
I’m experiencing similar issue with domain validation.
Domain: web.arena.tituto.com
Main domain tituto.com is managed by external NS server but web.arena.tituto.com is pointing to local NS server to which I have access.
Domain has two A records with different IP addresses (DNS round robin) but website is accessible on both of them. Server is IIS 10 and Lets Encrypt is being renewed by control panel (MSP Control) or by external software (https://certifytheweb.com/). Both of certificate requests (control panel and software) end the same. They can’t validate domain. IIS server logs show that there was external attempt of validation with 200 status from IIS server:
2017-10-16 09:58:09 91.219.122.191 GET /.well-known/acme-challenge/Kg-YkYXMtRXzyejWlVSwE8OyWfCndN_000LLLyrf-KU - 80 - 66.133.109.36 HTTP/1.1 Mozilla/5.0+(compatible;+Let's+Encrypt+validation+server;++https://www.letsencrypt.org) - - web.arena.tituto.com 200 0 0 564 272 179 -
this one is last example when I was trying to create certificate request from Certify app. Website has empty page and no redirects (web.config or .htaccess). Latest file in acme-challenge dir is still accessible:
http://web.arena.tituto.com/.well-known/acme-challenge/Js3PrTIxkwU-BWX9oPgzXm6TnNdx4cO18Q6TNWVHwPo
Any ideas what is causing this issue?