Please format your error message and give some additional information. This forum is run by volunteers and just dumping your error message here is not really motivating to help you.
Please check if you have included the path of opencv hpp files in "Project Properties ->Congig Properties --> C/C++ --> Additional Include directories"
Can you post your code here? Remember to use the preformatted text (Ctrl+K) option to paste the code or output of the compiler. To me it looks like you built a header loop somewhere. Like you include a header file test1.h which includes test2.h. And test2.h includes test1.h (and then you have a loop).
Please format your error message and give some additional information. This forum is run by volunteers and just dumping your error message here is not really motivating to help you.
I think this one is your problem (including more than once a header), please use
#pragma once
or the#ifndef...
stuff