This morning I lost external connectivity to my domain - I use a hidden primary and hurricane as published slaves.
I checked hurricane and it shows last checking of my domain on March 11 (9 days ago). All of my DNSSEC entries expired at week later (Mar 18).
I deleted the zone and re added it. If validates fine, but still shows "never checked" and that a zone transfer has not happened. I see the successful transfer in my Bind logs. I am not sure what's happening, but it looks like the service is not working.
I just signed one of my zone files, which triggers a script that performs the transfer process of the signed zone from my hidden primary (NSD) to HE's secondary DNS, and then checks that the transfer occurred.
The transfer took place without any issues.
So it seems that HE's DNS is working.