Not able to open User Interface

HI,
My asterisk box shut down unexpectedly 2-3 times, due to some power outage and other reasons, after that I am unable to access my User Interface that i used to open by typing my IP address in web browser.

10.20.30.40

What things i need to check in order to make it working back again.

Can i find something about logs ? or capture logs which will show me where is problem actually.

Sometime back also this problem occurred but its resolved by doing nothing.

Its critical issue please help !!!