I cannot locate my dad's phone

[AleksiDj52]

Hello everyone I want to locate my dad's phone. I opened GPS and WIFI (home) and it worked I opened Mobile data and close WIFI but it doesn't work I mean it's works with WIFI but with Mobile data doesn't work why?? my dad has about 200 mb (mobile data) can anyone help me?

 

[sharmi108k]

I think may be the signal strength might not be too strong.