is it your own WiFi signal if it is, is it been set with a password for protection preventing other users connection to your signal?
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=== Update ===
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Usually if it's able to pick up the wi-fi network but does not want's to connect is usually with the secuirity settings. you can try by deleating that as you defalt network and the se-activate it (try to reconnect to it) the default proiblem is usually the security settings.