IAP 1.18 failing to find most recent receipt on auto-renewing subscriptions

Nothing changed in this area at our end as far as we know, I just checked with the team. You are welcome to try 1.16 or 1.17, you can download from here Unity IAP Previous Versions (Obsolete - please see Package Manager) . Also, if you could provide the device logs, it would be helpful. Did you update the iOS version by chance recently?