For device logs, you can follow these:
iOS
Android
The Restore Purchases sends a request to Apple who then replies with a success or fail. Afterwards, if it was a success, the transaction listener will be receiving the restored purchases from Apple.
In your case, it looks like Apple successfully got the Restore Purchases request, but there was nothing to restore, so it didn’t send anything to the transaction observer.
In 4.5.2, you can validate this by seeing “Finishing transaction” in the Xcode logs for every transaction that Apple sent to the transaction observer. In 4.6.0, we reduced the output of these to only transactions that are valid (not expired/cancelled) and restoring something (reaching ProcessPurchase).
How are you testing this? Sandbox, TestFlight or live?
Does that Apple account / Sandbox account have any purchases made on it? If you are on Sandbox, make sure the Sandbox account is logged and not just the Apple account.
If you make a new purchase (subscription or non-consumable only) and then retry the restore transaction, does it go through the ProcessPurchase?