[wakeup command failed when on 3g]

wakeup comand works just fine when i try through my home network, but when i try through 3g i get a mesage saying "wakeup command failed". Also when i try to wakeup my pc from another wifi network i get a mesage saying "wakeup command sent" bbut the pc does not wakeup.  

 

Anyone know why is this happening and what should i do to enable wakeup from other networks? It kinda defeats the whole purpose of having an app that can wake your pc up remotely if i cant wake it except when im at home.

 

Thank you for any help that might come