External Forms return error page 404

Hello everyone,

I’m trying to integrate external forms for user tasks in my process.
I’ve tried following the documentation: documentation page
And also a few examples (which seem to be different, but I suppose because they are from different versions): task form external, generate jsf form
Still I’m not being able to correctly open external forms.
When in tasklist I click on the button “Open external Form” it always redirects me to a 404 page, even if the form page (a simple .xhtm page) exists.

Am I missing something?
Thank you very much for your help

Any update?