Errors
I noticed that my voting service is not working anymore, Hiveblocks too (now up). Wrongly, I blamed Hive developers.
I get error messages like missing active authority. Hive has bad error messages due to Steem heritage.
Let's Encrypt
In fact, it was because of the Let's Encrypt SSL root certificate expired. Let's Encyrypt is a certification authority that delivers SSL certificates for free.
The web servers and softwares should maintain an updated list of certificates from legit certification authorities. Outdated operating systems have to install the new Let's Encrypt certificate manually. Many devices will have browsing issues, e.g. old Android phones.
Free Hive Voting Service
I use SteemJS in my scripts, for Hive and Blurt too. After HF24, I could not use SteemJS for all operations. I made the minimal changes, using HiveJS.
I updated HiveJS as advised, but that did not resolve the issue. Unluckily, I have to change my code.
Steem and Blurt were not affected by the root certificate change.