I was having problems adding a C++ class I thought it was something I was doing a mistake but apparently something goes wrong when I added my PRODUCT_LICENSE_KEY, the new c++ classes that I added after that are not being added into the project , after I comment this line it works again:
contains(ANDROID_TARGET_ARCH, arm64-v8a) {
PRODUCT_VERSION_CODE=1011 # add 1 as suffix
PRODUCT_LICENSE_KEY = "XYZ...."
} else {
PRODUCT_VERSION_CODE=1010 # add 0 as suffix
PRODUCT_LICENSE_KEY="ABCD..."
}