I'm not so sure why everyone is on-board with blaming Oracle out of the gate. From one of the OP's comments, "Oracle support told him, step by step, to encrypt

I'm not so sure why everyone is on-board with blaming Oracle out of the gate. From one of the OP's comments, "Oracle support told him, step by step, to encrypt the database, which happened ages ago and is the root of all of this." That wallet is the responsibility of whomever created it. Just because it's empty now, doesn't mean it's always been empty. In addition to that, what if the person who initially encrypted everything with TDE, used a local only wallet? This would explain why the ewallet.p12 file is empty. Oracle recommends that you store your master key in the ewallet.p12 file and not the cwallet.sso file, which is the auto-open file, but only on the workstation it was created on. There could have been multiple failures here with multiple parties and not just Oracle.