Authentication Failed using Private Key,Public Key

[ios-52]

Hello
We are trying to connect our Mac and aws servers using the private key. but every time we got authentication failed.
Also, we have checked both keys on another application and it's working fine.so I think the problem is in the library. can you please help?

self.authenticationChallenge = .byPublicKeyFromFile(username: self.username, password: "", publicKey: "", privateKey: pvtfilePath?.relativePath ?? "")
self.shell = try? SSHShell(host: self.hostname, port: self.port ?? 22, terminal: "vanilla")
self.shell.withCallback { [unowned self] (string: String?, error: String?) in
                DispatchQueue.main.async {
                    if let string = string {
                        self.appendToTextView(string)
                    }
                    if let error = error {
                        self.appendToTextView("[ERROR] \(error)")
                    }
                }
            }
            .connect()
            .authenticate(self.authenticationChallenge)
            .open { [unowned self] (error) in
                if let error = error {
                    self.appendToTextView("[ERROR] \(error)")
                    self.textView.isEditable = false
                } else {
                    self.textView.isEditable = true
                }                
            }