Showing boxes manually

Hi,
another question.

I have a box with the ID 747 and to display them manually.
(https://kb.boxzillaplugin.com/showing-boxes-manually/)

<strong>Newsletter</strong>
<a href="#boxzilla-747">Hier anmelden.</a>
<a href="javascript:Boxzilla.show(747);">Hier anmelden</a>

In the Developer Console following message is shown :
VM2964:1 Uncaught ReferenceError: Boxzilla is not defined

The box will be displayed in either of the two examples .
Look an my site [tiles >> Termine]

greetingxxx form germany

https://ww.wp.xz.cn/plugins/boxzilla/