no appropriate default constructor

I am making a program and I am getting this error:
C:\trigger state.cpp(182) : error C2512: 'Sensor' : no appropriate default constructor available

What are the most common causes for this?

Not having a no argument constructor when one trying to be called? :)

Stuff like this..

Code:

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something instanceOfSomething;

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Will try to call the default constructor.

Post the code around the error and I can probably figure it out.

I am no longer getting an error