I wasn't familiar with the toolbox, but I downloaded it and everything seemed to work fine for me. My only thought is that perhaps you forgot to set it up so matlab can access files out of the different folders.
MATLAB - Documentation
The easiest way is to go to file -> set path
then click on the "add with subfolders..." button, then navigate to where you have the jplv7 folder, highlight it and click okay. Then everything should hopefully work.
If you can post most specifically what the errors say people can probably offer more help.