AuthState save and restore value

Question

I am building an app using AppAuth from OpenId. I am adding biometrics on Android in order to protect the app. My goal is to encrypt the AutState object, so when I am having the app in bkg, the AuthState object is cleared and I update it when I come back to the app when decyphering.

 private fun encryptAndStoreServerToken(authResult: BiometricPrompt.AuthenticationResult) {
        try {
            authResult.cryptoObject?.cipher?.apply {
                    val test = viewModel.authState

                    val encryptedServerTokenWrapper = cryptographyManager.encryptData(viewModel.getAuthState().jsonSerializeString(), this)
                    cryptographyManager.persistCiphertextWrapperToSharedPrefs(
                        encryptedServerTokenWrapper,
                        requireContext(),
                        SHARED_PREFS_FILENAME,
                        Context.MODE_PRIVATE,
                        CIPHERTEXT_WRAPPER
                    )
                 (activity as MainActivity?)?.onLoggedInFlowCompleted()
            }


        } catch (e: Exception) {
            viewModel.loginError.set("Error Biometrics")
        }

    }

the viewModel.getAuthState() is just returning AuthState object which is used by openID to save authorization req and response.

Any idea how to save this object and restore it. I tried the above code to save and the below one to restore but it failes

private fun decryptServerTokenFromStorage(authResult: BiometricPrompt.AuthenticationResult) {
        ciphertextWrapper?.let { textWrapper ->
            authResult.cryptoObject?.cipher?.let {
                val plainText = cryptographyManager.decryptData(textWrapper.ciphertext, it)
                callback.onSuccess(AuthState.jsonDeserialize(plainText))
            }
        }
    }

The AuthState object is defined as below:

https://openid.github.io/AppAuth-Android/docs/latest/index.html?net/openid/appauth/AuthState.html

Any idea how to make it works. I really just want to save the AuthState to avoid saving all object inside and restore it.

Regards Sebastien