As far as I know, I've not recently updated my Photoshop CC 2017.1.1 but all of a sudden the "save for web" interface (Cmd-Opt-Shift-S) wants to save my files in slices. I have NEVER, EVER done slices and have no idea why it would think I would want to. Is there some way to turn off this "feature"? I've been reading help tips for half an hour or more and everything refers to the 2015 release.
I'm going to guess that you inadvertently added slices to your file. You can do this a few ways:
So, moving forward... go ahead and show the slices as per JJMack, above. Right click over any slices with a blue badge and choose Delete Slice. Repeat until you are down to one gray badge. Then export again and let us know if that takes care of it.