Pico doesn't show images

I have a NextCloudPi instance (NextCloud 20.0.4, NCP 1.34.7). Until recently everything was OK. I just installed several themes (clean-blog, default-blog, travelify) for test, enabled proxy in apache2 for short addresses on my NCP and enabled proxy on the other server with nginx to use address for the site like www.mysite.com.

I found that blog themes don’t control the images scale. I’m completely new to html and css to edit the files of the themes and I decided to try also magazine theme with its plugins. Then something happened (I don’t remember other changes).

For the now I can see images posted in .md files only in travelify theme and only using www.mysite.com. In other cases I see text string like “IMG_5656.jpg” instead of the image.

What am I doing wrong?