let's encrypt renewal fails

I received a notice that the certificate for one of our websites is not renewing. The challenge file is available from a browser but manual renewals also fail and you are returned the “Current Certificate” tab with no warning. When you go to the “Let’s Encrypt” tab you get the error message below

crypto-organics.com challenge did not pass: Fetching https://crypto-organics.com/.well-known/acme-challenge/kBQVSwGTelOwRv1Lqb0F6uoqIJxDgH384HeHCYq4DW8: Error getting validation data

I was running out of time but could not get this to resolve. In the end I installed a self signed certificate then did a new let’s encrypt certificate and it worked, I am concerned that this is going to happen on multiple sites.