YASARA plugins use the Python scripting language. If Python is not installed, these plugins will not be loaded and some convenient options will be missing in the menus (e.g. to get PDB files from the web). Just click Help > Install program > Python to install it, or alternatively download Python from www.python.org . You need to restart YASARA afterwards.

An alterative explanation is that your computer is running short of swap space and YASARA cannot run Python. Look here for more details.