Assuming you are referring to a car's side view mirror:
There are a few things that could be causing your power side mirror to malfunction. First, check to see if there is any debris obstructing the mirror or the mechanism that moves it. If there is, clear it away and try moving the mirror again. If the mirror still doesn't move, there may be an issue with the fuse that powers the mirror. Check your car's fuse box and look for the fuse that corresponds to the power side mirror. If the fuse is blown, replace it with a new one and see if that fixes the problem. If the mirror still isn't working, the problem may be with the mirror itself. In this case, you will likely need to take it to a mechanic or car dealership to have it repaired or replaced.