This Relay option encrypts the file in your browser before it enters the live transfer. For now, the recipient needs to open the link in the Chrome or Edge desktop browser to decrypt and download it.
Native PhotonFile desktop apps are coming and will remove this browser-specific Relay limitation.
If your recipient cannot use Chrome, use Photon Vault for persistent client-side encrypted storage, sharing, and Secure Inbox workflows, or disable client encryption before starting this Relay transfer.