When doing a snapshot backup and the client encryption key is longer than 16 characters the following error is shown (backup fails but account is disabled):
Failed to backup: cipher init failed: No installed provider supports this key: javax.crypto.spec.SecretKeySpec
This is because of US export restriction policies built into the Java Runtime environment from Sun/Oracle that is shipped with the Backup Client. This will be the case for Client v184.108.40.206 and older. Even if a client has a higher version but has been auto-upgraded from v220.127.116.11 or lower, the problem will remain.
There are two ways to fix this.