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/Gf7ty_Q2cGGqhcywT0Qmr_kjHy6F5EawW5u_aMSx3vg: Timeout during connect (likely firewall problem)