debug - step-into a library function

I downloaded an open-source project (c++ project).
It includes a library which has its own CMakeLists.txt.
It also includes an example, with a main() and its own CMakeLists.txt. It includes:
for the library.
It runs ok and I can debug the example.
However, when I try to step-into a library function - it doesn’t.
Can you please advise on what might be missing?
Thank you

The library function may be optimized away?

More details would be helpful though.

As it uses find_package you have built the library before the example, did you build it as debug? The library might default to Relase?