widgets not working?

I am extremely new to this whole website design and most things tend to go over my head. But I did have functioning widgets and now no longer do? I have followed several youtube videos that have walked me through how to set up my site and get my blog started. I have followed the instructions to add a “subscribe” widget as well as a “facebook like” widget and followed step by step but nothing is appearing? And even when I’m in my “customize” section and I’m adjusting the widgets on my sidebar and should be able to “preview” the changes, nothing happens? Have a disabled something without being aware? Not sure what to do as all this is very new. Any help would be greatly appreciated!