use erase button on find my iphone app on my jillbreaken iphon 4 and when found it turn it on it last only four 30 seconds or less and then it turn off randomly wht should plz help

I use erase button from find my iphone app bye mistake .. On my jillbreaken iphon 4 and when i found it... i turn it on it last only four 30 seconds or less and then it turn off randomly .i tread every thing even i tread to erase it but the erase process didnt complete ..wht should i do plz help me