Check that your phone is able to receive notifications e.g. not in airplane mode, receiving network coverage and notifications are activated for the SecureIdentity app.
If you are receiving good network coverage then please check your devices individual notification settings and ensure that the SecureIdentity app is allowed.
If you are using a 3rd party security app e.g. 360 Security you may need to also refer to this if all device setting are correct as these can interfere with notifications being received.