Hi i need a service manual for the canon powershot sx40 hs

Simple diagnosis, battery is not powering the camera. There are many possible reasons. If you value you camera, don't attempt anything - simply bring it to a compatible licensed service agent for a check up.

check out this link Canon PowerShot SX40 HS PowerShot SX40 HS Camera User Guide

and this Download Canon Powershot SX40 HS Getting Started Manual

Assuming you have charged the battery to full. If you did not use the camera for a long time and left the battery inside then the battery terminals may have corroded.

Check user manual for possible problems with battery when left for long periods without charging.
https://www.lclark.edu/live/files/14568-canon-powershot-sx40-hs-manual

Try installing the software that came with the camera on your computer first, then connect the camera to the computer.

some camera will inactive the electronic view finder if you shot through the lcd monitor, try to find out in the manual book about shooting trough view finder.

You may download the manual and more from here.

I own a same model camera but the problem you mention is new to me. I would try re-setting individual menus to their defaults first, then switch off the camera for sometime then re-start. This time, try the factory re-set option. This is no definite solution to your problem, but it;s worth trying because I had a smaller (pocket-size) Canon camera sometime back that worked that way.

Try the procedure in this tip.

Try the procedure in this tip.