Extra options missing in theme options Portfolio / Slider / Professors / etc.
When I go to the theme options and select for example professors, then I only see:
> Theme Options > Our Professors > Enable on ... Homepage / frontpage, Entire site... etc.
The same with the Featured Slider:
> Theme Options > Featured Slider > Enable Slider on ... Homepage / frontpage, Entire site... etc.
All the other options that should be there are not displayed!
My problem is similar to this one: https://catchthemes.com/support-forum/topic/change-content-on-courses-professors-etc/
So I have deactivated the plugins. And then I DID see the other options besides only "Enable slider on..". So I changed the settings of the slider. I tested the site. Returned to Theme Options and then the other options are GONE Again! I cannot deactivate any other plugins. Deleted the theme and installed it again. But still no result, I do not see the other options.
I have tested it with Google Chrome and with Firefox. Both do not display the extra custom settings. How can I fix this? Please help!?
(The domain of this site is a temporary development domain: http://www-d-o-t-pabn-d-o-t-nl.alvast-online.nl/)