Hi rbenmess,
Thank you for your post and for using fuzzylite.
please check and follow the instructions on https://github.com/fuzzylite/fuzzylite#compile-link-and-execute.
I suggest you first try linking statically because it is easier to make sure that the library is found and loaded. Make sure the compilation flags shown in github are correctly added to the project properties.
Alternatively, you can use CMake to create your project automatically based on the example application at https://github.com/fuzzylite/fuzzylite/tree/release/examples/application using cmake -G Xcode . from the example application folder. Then you can explore the differences with respect to the project you have created.
Cheers.