Error code 415 when I invoke an action through Api

Hello!

I tried to invoke an Action using html, as I read on appsheet doc, through an Automation (in the email sent to user). The objective is to change the value of a field directly using the button from the email.

But, when I click on the button in the email I receive, a new page is open with the http error 415.

Please, could someone help me on this error? What is wrong in my code?

Thank you for your help!

Regards!

Ruxandra