As you can see, the unencrypted backup is useless once you've used the encrypted wallet to generate new keys.
That's not entirely accurate: The coins that were already in the wallet before encryping it are still there, also in the backup. But the moment you use a new receiving address, or create a transaction which sends funds to a change change, those aren't in the old backup anymore.
That's why "
backup" is mentioned, I didn't mentioned anything about the previously received bitcoins in the unencrypted backup.
The point is the newly generated keys wont be recoverable using the unencrypted backup.
Based from OP's situation, it looks like the case.