When trying to connect to https://my.gov.au - which is the national client portal for all things related to the Australian government - Orion on Mojave now says the certificate is not trusted, even though it has a current valid certificate which works fine in both Chrome and Firefox. Safari 14 produces the same error.
Perhaps I need to update some certificates, and if so, how and which ones?

I expect it to connect securely
130.2
Mojave (10.14)