This change won't be noticed by most users and there is nothing you need to do. A new SSL certificate has been deployed to help users on devices that were unable to connect recently. If you have issues logging in to jammr over the next few days, please let me know.

The new certificate is issued by GlobalSign/AlphaSSL while the old one was issued by Let's Encrypt.

Thanks to Bo for reporting the problem and to HighAction for helping troubleshoot it.