If your Instagram connection is disconnected, your authentication token may have expired and you need to reconnect the Photo Gallery widget to Instagram and re-authorize your credentials.
To reconnect the Photo Gallery widget to Instagram:
Click the Photo Gallery widget to open the Content editor.
Click Connect Instagram.
Type your Instagram credentials, and then click Log In.
Click Authorize.
For more information about Instagram Feeds and the Photo Gallery widget, see Instagram Feed and Photo Gallery Widget.