Hello, great job. I already deployed the demo version "wt-pdf-viewer-demo"

Hello,
great job.
I already deployed the demo version “wt-pdf-viewer-demo” and run it on Mozilla Firefox Quantum 66.0(32-Bit). Every thing works fine. But when my application runs on the same Browser it’s not able to print. Further the thumbnails show only silhouettes. On Google Chrome Version 77.0.3865.75 (Offizieller Build) (32-Bit) the behavior is the same. I tried to follow the instructions strictly as in demo showed but obviously something seems to fail. On Internet Explorer 11 Version 11.1217.16299.0 every thing seems to work fine either “wt-pdf-viewer-demo” or my application.
Can somebody please help me?
Thanks in advance…