did you start from the jevois sample module? If so, you need to edit your CMakeLists.txt to link against the jevoisbase library, since BlobDetector is implemented in that library.
There are some explanations in the CMakeLists.txt, please see
https://github.com/jevois/samplemodule/blob/master/CMakeLists.txt
typically, you would need to uncomment the commands link_directories(), include_directories(), and add jevoisbase as a dependent library in the list in target_link_libraries()
If this does not work, please email us your source code (the whole module directory) and we will help you.