Thanks for getting in touch. It seems to be timing out after 20 seconds, which sounds like a TCP level timeout. Is the network between the tentacle or server slow or flakey (eg 3G)?
It looks like a listening tentacle, so could you run through this guide and see if that turns up anything?
The SSL handshake between the server and tentacle is completing, so the first few parts of that doc probably don't apply, but it is still good to run through it just in case it turns up something.
Also, once you have done that, could you turn on trace logging for both the server and tentacle, retry a health check to that tentacle, and then send me the server and tentacle logs for that time period? Trace logging should log the individual requests made over the connection.