Sliders(Megaslider pro , Masterslider) do not work (with Zuki theme)

Hello everybody. I use the theme Zuki from Elma studio. I want to run a Slider. I installed Mega Slider Pro and in the preview everything is fine but not on site – upright fotos are not resized and make the slider look weird thumpnail navigation does not show. I tried Masterslider and it is the same: in the preview its fine and nothing shows on the site.
So I am guessing there is maybe a JS Problem?
I need just some Ideas where to search and what to do to find reason why the sliders dont work or I even would be happy to find a slider that works.
I cannot deactivate all the plugins to see if one causes the trouble – since at the moment the site is highly frequentetd and the plugins are in use.
Ive looked for similair threads but did not find any.