public post preview not showing up in new post interface

I used public post preview before but some wordpress update has broken it for me.

It does not show up as it should (does not look like your screenshot https://www.ads-software.com/plugins/public-post-preview/screenshots/). Just as if it is not installed.

Another admin can see it if he is logged in. So I thought perhaps it is a browser client caching issue? To exclude that, I deleted tried again with a fresh browser profile. Did not help.

So maybe it is a user setting that got somehow messed up? I created a new admin account, but still, public post preview does not show up on the wordpress new blog post interface.

Apache error log does not show anything.

Any idea how to fix this?