So autofs randomly stopped working on one of my Ubuntu hosts (this issue has been found on Arch as well so its most likely a change upstream). I found this error in the logs:
attempting to mount entry /net/freenas.example.net get_exports: lookup(hosts): exports lookup failed for freenas.example.net key "freenas.example.net" not found in map source(s). failed to mount /net/freenas.example.net
The fix was to replace the following line in /etc/auto.master from
/net /etc/auto.net --timeout=60
and then restart autofs (sudo service autofs restart).