OK .. what happened?
Problem: Widget SIDEBARS did NOT show
1) for nearly 4 hours I've tried to get the Widget SIDEBAR to show. Nothing. The site would crank for 10 minutes, then nothing.
2) I read the question by esmi above - asking if the error was still found in Theme 2014. I tried it - but w/ NO intention of changing themes. Same thing. No Widget Sidebar.
3) I began writing up this error report - went back to check on a name - and VOLIA! there is it is ... seemingly working.
4) I filled in the code for the new widget, in the appropriate sidebar. But nothing. It took at least a dozen tries: total cache clearing didn't work: but finally I cleared the entire widget sidebar block, saved as 'empty'; displayed on the site and had a total removal of the widget sidebar element. I then refilled the element, saved and looked. Finally a correct widget sidebar element.
I'm glad it's working. But seriously wondering What Else is going to crap out. ???
As well, I can't say I'm overly thrilled and awed by the new design either. It's pretty bland, and I don't personally care for 'dark backgrounds' on any Admin Work area. It's not only 'not that cool', it's not that legible, either.