I just completed installing a new SSL certificate for NG. Hopefully, the transition from the old certificate, which was to expire soon, and the new one valid until August 2023, will go smoothly.
Should your browser object to the "new" https, please report the issue in the Site Help section. It might help to clear any NG-related cookies as well. Our forum only sets a login cookie, so there shouldn't be much to purge anyway.
/Birna