Preview not working

[p-o-seidon]

Describe the bug
I used the slide as shown on https://mszturc.github.io/obsidian-advanced-slides/templates/#how-to-use-templates. When I press the preview button, the note splits and on the right hand side appears the slide in ascii format instead as a preview:

`

This header will be part of the content section defined in the template

Everything define outside a block will be placed in the content section.
Therefore every template has to contain at least a content variable.

To place a text into the footer section you have to create a block comment with the name of the variable you defined in the template.

::: footer

This header will be placed in the footer section of the template

:::`

"Open in browser then just says "Open Presentation Preview in Obsidian first!" in the browser.

IS there anything I have to install to make this work?

I am on Linux (EndeavourOS).

Samples to Reproduce
As described a bove.

Expected behavior
I'd expect the slide preview as shown in demos and videos.