Question:  How to fix "Error fetching applications" after spinnaker successful installation?

Answer: As a security measure, default spinnaker installation allows for local access only. The Browser need to reach deck (UI) and gate(API gateway). The procedure for exposing Spinnaker outside of local host is provided in the link below.

Note that if its a debian install, please check if gate is listing on the expected port by using the command:  ps -ef | grep 8084 (8084 is the gate default port number) or netstat -ntlp command.

Accordingly need to change these files to allow gate and deck to accept connections from anywhere:

echo host: 0.0.0.0 > /home/spinnaker/.hal/default/service-settings/gate.yml

echo host: 0.0.0.0 > /home/spinnaker/.hal/default/service-settings/deck.yml

These links may help: 

https://blog.spinnaker.io/exposing-spinnaker-to-end-users-4808bc936698

https://www.spinnaker.io/setup/quickstart/faq/