Unable to take the user to Google Pay screen with TapAndPay

I'm trying to integrate Google Pay SDK in a project. For achieving this goal, I need to generate an object and pass it to a built in method. After that, SDK is responsible to take the user to Google Pay screen, but the google pay screen does not pop up. Here is the code I've written:

  val userAddress = UserAddress.newBuilder()
                .setName(it.userAddress.name)
                .setAddress1(it.userAddress.address1)
                .setLocality(it.userAddress.locality)
                .setAdministrativeArea(it.userAddress.administrativeArea)
                .setCountryCode(it.userAddress.countryCode)
                .setPostalCode(it.userAddress.postalCode)
                .setPhoneNumber(it.userAddress.phoneNumber)
                .build()
            val pushTokenizeRequest = PushTokenizeRequest.Builder()
                .setOpaquePaymentCard(it.opcBase64.toByteArray())
                .setNetwork(it.cardNetwork.ordinal)
                .setTokenServiceProvider(it.tokenProvider.ordinal)
                .setDisplayName(it.userAddress.name)
                .setLastDigits(it.lastDigits)
                .setUserAddress(userAddress)
                .build()

            tapAndPayClient.pushTokenize(
                this, pushTokenizeRequest, 1
            )