A test authorization for jonrowlison.com to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
Fetching http://jonrowlison.com/.well-known/acme-challenge/VqHNPe_w8irbTJz3vmJUBPUCCeWsRUc3TSETh2JiHy0: Timeout during connect (likely firewall problem)