To figure out the issue, you need to look at the parameters of the x-via header for the AMP pages. In your case, this is what you are getting: x-via: speedwp/origin,qs
Essentially, the x-via header tells you that you are using APO (speedwp), but that the content was NOT cached and returned from your web server (origin) because it has a query string (qs). In your case, the query string is ?amp= at the end of the URL. Right now, I believe APO is NOT caching pages with an ?amp query string. It will only cache AMP pages if they use the /amp/ slug.
I know @yevgen and his team have recently added some query strings to be safely ignored and cached by APO, and I think adding query strings for AMP pages would also make sense since not everyone uses the /amp/ slug. I know the developers of the Official AMP Plugin for WordPress are leaning towards an ?amp query string rather than the /amp/ slug, but discussion is still ongoing (https://github.com/ampproject/amp-wp/issues/2204).
So for the time being, if you want to be able to cache AMP pages with an ?amp= query string, you could always setup a Page Rule with a Cache Level of Cache Everything and the following URL match: https://lamiacasaelettrica.com/*?amp=
Hope this helps.