Tignan mo po kung may firewall settings sa Wifi Portal if wala naman, try nyo po yung Family Link ng Google.
Bale, Yung phone mo yung parent account/Gmail then gagawan mo sila ng Children Gmail Account na under nung Parent account mo. Pwede mong kontrolin yung access nila sa apps at internet gamit yun.
Note: Wag mo pong gamiting File Storage yung Children Gmail kasi need mong burahin yung Gmail account After nilang mag 13 or kung kailan mo gustong alisin yung monitoring nung device nila.