Home Slider doesn't work

Hello everyone,

I go to Appearance > Theme Options > Homepage Content (where months ago I set up a unique static image in the slider) and when I try to modify the image or add new images, nothing works. I click on several places but everything remains the same, no windows pop up so it looks like is broken.

I’ve seen it could be a conflict with a plugin. I will check that but I was wondering if anyone could tell me where I can amend the slider in the code please? Not format but add/delete images.

Thanks in advance, A.