A simple repair of the software will reset all your settings and customizations bringing you back the original functionality of the software, including the Collage button that is hidden. In case this approach is not working, I suggest that you should download a new package of the program and perform a fresh installation. Also in this case, a restart of the computer is always welcome. After that you will see that the button which was missing is in its place and working. This problem could happen due to the fact that another software messed up some libraries and settings.