What could be the reason for a Google Action with external endpoint (API) to work on the Actions Console Simulator, but not as deployed? - actions-on-google

Question

I am new to the whole creation-process of Google Actions.
I created an Action with the new Action Console.
It has an fulfillment endpoint to my server (as example: www.mypage.com/api).
For testing purposes it has no authentification, so it generates a public API response.
Said API generates a simple JSON response based on a send event handler.
In short: Action onEnter sends handler to API, API queries SQL database and sends the response back to my Google Action that then "speaks" the SQL result.
The result with the Actions Console Simulator is:
Testing with "Smart Display device: everything works.
Testing with "Speaker (e.g. Google Home): everything works.
Testing with "Phone": main intent is invoked and text is shown but does not get spoken.
So i tested the command "Hey Google, talk to the unicorn app" directly on my smartphone.
Here **everything works fine ** as said smartphone has the same e-mail like the one on my Action Console account: it recognizes the main invocation command and when i ask by voice to get the data, the data is received from my server and spoken.
So something is wrong with the "Phone" device in the simulator. This has been confirmed by me from other users saying that they often have trouble with the simulator function correctly.
I then deployed my Action.
It was reviewed and approved.
A few seconds later i received an auto-email saying that there were too many errors with my app, asking me to check its health status. I did so and in the Health tab, i can see that it has an error but it does not show me what the error is.
THEN I CONTACTED A ACTIONS-ON-GOOGLE EXPERT
They helped me a lot into the right direction but could not go deeper into the problem as my connection (the endpoint API) is outside of their servers.
So i ended with their tip on checking the Google Cloud Logging Console.
As said Logging Console is also new for me, i learned on how to query my results but:
How can i query for the so called "is_health_check" flag?
I am asking this because the Google Expert recommended me to search for said flag but i do not know on how to query it.
Sorry for this ultra-long entry but i am trying to be as transparent to you as possible, as i have been trying this out for several days now.
Thanks in advance for your time, ppl!

Answer 1

So the error is simple once that you know how Google handles the external webhooks. Thanks to the help of 2 Actions-On-Google Experts i was informed that Google pings your external Webhook from time to time.
As soon as they get an error as result from said ping, the Action will be deactivated from the Assistant until a new ping response sends that everything is fine again.
My problem was that after deploying the action and while it was under reviews, i continued to work on the code on my server. While coding, the Google server pinged and received an error code.
My fault, but at least i learned the thing about pinging your action!