I am unable to install and run legappend

Here's what i did:

downloaded and unzipped legappend (to a folder on the desktop)

used pathtool to create a new search directory to the folder

set the MATLAB workspace folder to the folder containing the demo

ran the demo

and i get these errors:

 Error using legend (line 120)
 Invalid argument. Type 'help legend' for more information.

 Error in legappend (line 74)

     [legend_h,object_h,plot_h,text_strings] = legend(h,allDatah,str);

 Error in legappend_demo (line 85)
 legappend('my new amazing model!')

 Error in run (line 96)
 evalin('caller', [script ';']);

Can anyone help me understand where I'm making the mistake?

I appreciate all the help i can get!!!

Thanks,

Josh