DEBUG: wp_remote_get to
DEBUG: arguments: Array ( [timeout] => 5 )
DEBUG: error getting URL:cURL error 28: Connection timed out after 5001 milliseconds
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.