In users' personal sites pages(/user/xx/so/dashboard), user bar and dockbar are not accessible from any user without the power user or administrator role. In every other site's page, users can normally access it without these 2 roles. Why is this happening?
This issue was resolved by creating a hook that assigns automatically the Power User role on every newly created user.
A Liferay staff member told me that Power User role is required for all social office plugins, sites etc. liferay post