Problem with kernel sources in FreePBX 14

I made a fresh installation of the latest FreePBX distro. I also install an openvox B100E BRI card.
I upgrade the whole system and then tried to install openvox DAHDI drivers as described in openvox wiki page (cannot put link because I am new user)
I have made this procedure many times succesfully but this time I have problem with kernel sources. When I type “make” in dahdi directory, linux complains that missing kernel sources even though I have installed them with command “yum install kernel kernel-devel”. What am I missing? Any suggestions please?