Outside PIR light with no switch?

HI - would really appreciate some advice. I moved into a new house recently and noticed an outside PIR light next to the patio doors on the back of the house, which does not come on at all. I assumed it was switched off but have checked and there seems to be no switch controlling it - it is a tiny house and I have tried every switch I can find!!! Is this possible? If so, could you suggest what I could do (apart from checking the bulb which seems fine) to see if the unit is damaged, or simply deactivated somehow. If it is a problem, or it needs replacing, I will get an electrician in as I am useless, but would like to avoid total embarrassment if it is common problem and I only need to do something simple!

Many thanks, Floss112