No JSON received

My site is offline yet,
but i am not able to use the json content importer.
My json feed is public:

https://plus.pul.it/avvisi/avvisi.json

But the plugin is not able to read json from it.

Could you help me?

Error generated is:
DEBUG: wp_remote_get to https://plus.pul.it/avvisi/avvisi.json
DEBUG: arguments: Array ( [timeout] => 5 )
DEBUG: use fallback2cache: 3
DEBUG: fallback2cache failed: no cached JSON found
DEBUG: no data received: check url of json-feed
EMPTY api-answer: No JSON received – is the API down?
Check the API-URL in the Block-Settings, please.
Use “/json-content-importer/json/gutenbergblockexample1.json” as example. You might switch on the debugmode on the right side.

The page I need help with: [log in to see the link]