I just started building our webpage and I do encounter a similar problems like in old threads – I uploaded several pictures to the slider, but on the mainpage they are not showing up.
Hope you can help me with that topic (webpage snacargo/wordpress)
Please follow these steps and check if slider works for you.
1. Create home page
2. After that go to Settings -> Reading and assign front page like this http://nimb.ws/K3iGYl
3. Go to Appearance -> Customize -> Featured Slider and enable slider like this https://prnt.sc/jrg4q7
If this does not work, please provide us your site URL.