Issue
You have the error "Encryption key is invalid" on your backups
Resolution
When this error occurs you will need to re-enter the encryption key for the relevant backup set.
When logging into the obm and going to backup sets and selecting the backup set you should be prompted to enter this and then the error will clear.
We do not keep a copy of encryption keys this side so these should be documented somewhere when the backup was created.
If you have been logging into the obm as a different user sometimes the wrong key may be cached. To resolve please close down the obm and then delete the .obm folder (C:\Users\*username*\.obm) and re-open the obm and login.
If this still does not work and you do not have access to the correct key the next step would be to create a new backup set to backup the data covered in the original set.