Fatal error: Call to undefined function

Dear,

I installed Webyp on the server with the online tool,
and use it within Rapidweaver 5.0

When inserting a webyep page,
I always get this error when I try to acces it online
Fatal error: Call to undefined function webyep_shortText() in /home/content/48/11284948/html/page11/index.php on line 335

The iste in question is here
http://performance-maastricht.org/page11/index.php

Any suggestions? Checked the installation of webyep on the server and that seems fine (also the permissions on the data folder seem to be ok)

Thanks!