FSTL400 - Invalid Response From the Fastly API

Agent error code #FSTL400 indicates the API answered successfully but the body was not the JSON the agent expected.

Common causes include:

• An API base URL override points at a proxy, captive portal or login page that answers 200 with HTML
• A TLS-inspecting proxy rewriting responses

Steps to Resolve

1. Clear the API base URL field unless you deliberately need an override, which leaves the agent using https://api.fastly.com
2. From the agent host, request https://api.fastly.com/service with the API token and confirm the response is JSON rather than an HTML page
3. If a proxy sits in the path, exclude the Fastly API from response rewriting

Still Having Issues?

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