M'è venuto pure il dubbio che ci fosse qualche problema sull'hardware, ma ... ho caricato il classico esempio WiFiWebServer e ...
Attempting to connect to SSID: xxxxxxxxxxx
SSID: xxxxxxxxxx
IP Address: 192.168.1.172
signal strength (RSSI):-37 dBm
new client
GET /index.html HTTP/1.1
Host: 192.168.1.172
Connection: keep-alive
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.98 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding: gzip, deflate, sdch
Accept-Language: it,en-US;q=0.8,en;q=0.6
client disonnected
... funziona regolarmente 
Guglielmo