Why will my Canon PowerShot A460 not power up?

Your problem still may be the batteries. If the battery slot is dirty it will not function. You will need to clean the battery slot using the Battery Installation Guide so you can properly remove the batteries to clean the slots.: Canon PowerShot A460 Battery Replacement

The problem maybe just as simple as you inserted the batteries

wrong or the battery slot isn't closed completely.

If its not the batteries your power button may be broken. If you tried multiple times to turn it on and it doesn't, you will need to remove the back case by using the Back Casing Installation Guide: Canon PowerShot A460 Back Casing Replacement

If your camera will not power-up after you checked all these possible issues, it may be a more severe problem. Take your camera to a professional or where you bought it.

I hope this helps.