Hi Nastia and Bojan,
while deactivating all other plugins didn’t have any effect, I noticed that changing the theme does something. I mean at first I tried two other themes and when also no sidebar was showing, I gave up. But later then, I tried some more themes and suddenly with one of them: there was a sidebar again! Strange! It seems like your plugin has a problem with more than just my theme, I suppose Erik uses some other theme as well and has the same issue.
My theme is “Pinboard” by the way. Could you guys please try your plugin with that theme?
Thanks, Kenny