Receiving the error
"Preparation for upgrade to 10.8 failed. This is not a valid zip archive, or the digital sugnature is corrupted or not found."
If you read the release notes for 10.80 you will see that for the curent release automatic update of RASes is not possible. This is due to a signature change on the binaries (installer, upgrader). While central 10.80 can be made aware of this signing change and made to accept this change, the older products cannot be made aware of it. The change requires both some code changes and keystore changes on the RAS side in order to make it aknowledge the new signature.
As such when upgrading from OO 10.60 or 10.70 to 10.80 or later you will not be able to update the RASes automatically., however when going from 10.80 to any later OO version it will be possible to use the automatic update.