Deck will not connect to Gate. Receives 403 Error.

Issue

Deck will not connect to Gate, all GUI aspects of Spinnaker are not working as expected. This can happen during the initial installation, or possible later on if infrastructure changes or configurations are reset. This is particularly noticeable for organizations that run tight internal network security and firewalls. 

Cause

One of the causes of this can be internal firewall infrastructures. Certain organizations have very restrictive firewall settings that require very specific URLs to be opened up so that Spinnaker can work as intended. Note: This is an esoteric issue, please check with organizational ops and infrastructure teams to ensure this is relevant to you.