Oh right,
Yes that’s right, using “sections” will disable the sidebar as mentioned in its documentation here:
https://docs.generatepress.com/article/sections-overview/
“Enabling Sections on the page will remove the default editor, and will also remove the sidebars from your page.”
If you need the sidebar displayed, consider using GenerateBlocks’ Container Block or Grid Block for content sections instead of the Sections module.
A wise man once said:
"Have you cleared your cache?"