I have GeneratePress Premium installed along with Lightweight Grid Columns. I create a page, turned on Sections, and then Edit a section. I click on the button to add columns and nothing happens. However, if I click on the same button while inside the Visual Editor or SiteOrigin Editor widget, the columns window pops up just fine.
Thanks for the tip. The conflict was with Page Builder by SiteOrigins. If that plugin is activated, then the columns button doesn’t work inside Sections.