Getting " " (empty) Decrypted string from update function

[nirav-kotecha]

class func decrypt(encodedData: String, secret: String, algorithm: String) -> String {
        do {
            let key = Array(secret.utf8)
            let bytes = encodedData.hexaBytes
            let cryptor = try Cryptor(operation:.decrypt, algorithm:.aes256, options:[.ecbMode, .pkcs7Padding], key:key, iv:[UInt8]())
            if let decrypted = cryptor.update(byteArray: bytes)?.final() {
                return String(bytes: decrypted, encoding: .utf8) ?? ""
            }
        } catch {
            print(error)
        }
        return ""
}

i am using above function to decrypt data. it will returning blank "" string.
i am using .ecbMode and .pkcs7Padding pattern
also i am getting key and bytes data successfully. issue in cryptor.update function.