Slider doesn't show up (phone, tablet)
If you can't even see an empty space, where the slider should be, then you might have put it into a php code/module position, which doesn't load in phones. In Android Chrome you can check the website's source code, if you write view-source: before the url of your page, for example:
Then if you look at your website's source, you can see, where the slider's code should be, there are a lot of n2, ss, nextend and smartslider words, so look for them, and confirm that the problem is with the slider, or the position.
If you are a more advanced developer, this documentation could help more.