There is an explanation why it might not work. Has anyone gotten this to work nicely with Plone?
In order to trigger Always Online, your web server will need to be returning a standard HTTP Error code of 502 or 504 timeout. Always Online will also work when we encounter issues contacting your origin (Cloudflare Errors 521 & 523), timeouts (522 & 524), SSL errors (525 & 526) or an unknown error (520). Always Online will not be triggered for other HTTP response codes, such as 404s, 500, 503, database connection errors, internal server error, or empty replies from server.