We have updated the Adafruit IO SSL/TLS certificate. There is one library that has a fingerprint to allow devices using the esp8266 to connect securely.
If you are having issues connecting, please ensure you have the latest Adafruit IO Arduino library:
https://github.com/adafruit/Adafruit_IO_Arduino
The certificate is fingerprinted in that library and you will have issues connecting if that library is out of date. The current version with the latest fingerprint is 3.7.0.
If you are using the Adafruit Feather M0 WiFi (ATWINC1500), you will need to update your SSL certificate manually. Please follow the guide here: https://learn.adafruit.com/adafruit-fea ... rtificates
In the future, we will announce this much further in advance to ensure everyone is aware of the scheduled certificate updates to reduce downtime. The next update will be in approximately 2 years. If you had any significant downtime or are having issues getting connected again, please reach out to us, and we can assist you.
Also, there is an example that was updated in the Adafruit MQTT Library. The latest release for that is found here:
https://github.com/adafruit/Adafruit_MQ ... /tag/1.2.0