Hm if you installed the program from the sources it should work, though you may also need to install the development packages for Gtk, etc.

You can see the whole process in this video i took a couple of years ago:

https://www.youtube.com/watch?v=s_01Xhd2EJM

(this is making a simple puzzle game)

I'm basically doing the same procedure for many years now and i never had an issue with getting Lazarus or any of its packages to work.