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/h-Rb-owS1Dv8D5MDEd072o0CP2he6-ruZu1_mmWHDxI: Timeout during connect (likely firewall problem)