Security Link reference code 503, message “Authorization Denied - Failed to Receive a Certificate”

This indicates there is a problem with the Wi-Fi connection. 

Here are some things to check:

1. Ensure you have a strong Wi-Fi connection on your diagnostic tool.
2. Try using a different known good network.
3. Move vehicle and diagnostic tool closer to router Tool may pass Wi-Fi test and still not be close enough to router.