Looks like its an issue with their cert. I had to follow steps from this thread to get it working. I think it was just a matter of installing a HACS package and a few quick command lines and a reboot. Wasn’t too hard. I can’t remember all the steps.
Thanks for that - appreciate the info!
I guess I’ll wait for the fix to make it into a public release rather than mucking about in the docker containers, though.