Error: SecureChannelFailure (The authentication or decryption has failed.) #2672 was my speculation to several sudden Jottacloud failures. No response there yet, and Jottacloud just tolerates (I hope) the use of reverse-engineered third-party access such as this, so they might not announce any change that well.
Error: SecureChannelFailure (The authentication or decryption has failed.) can be another one to watch.