If i'm looking on the expiration details for the Certificate it says,
Tue, 05 Oct 2021 23:59:59 GMT
so it is expired but like
@Wyldanimal mentioned already just click on the advanced Button
and choose "Accept the Risk and continue".
By the way you can always use a Condom for the Web in form of a
Script Blocker like NoScript,
https://addons.mozilla.org/en-US/firefox/addon/noscript/
or uMatrix.
https://addons.mozilla.org/en-US/firefox/addon/umatrix/