TOC is not shown on post pages

Hi there,

Today I installed this plugin and for some reason I can’t get it to work.

I tried the auto insert mode for blog posts, but it did not appear on the post page.
Then I tried to add it via a shortcode, but this did not work as well.

Here is the shortcode within the blog post:
https://d.pr/i/3QIlr4.png

And here is the fronend:
https://d.pr/i/EhiuVq.png

I disabled the cache plugin, so that should not be the issue.

I also disabled all the other (not necessary) plugins. Here are the remaining:
https://d.pr/i/lSRCzS.png

How can I fix this?

The theme is uncode.

Regards,
Zoker