Octane's Scatter on Surface Feature doesn't work as intended in the version 28.14 stable and 29.7 alpha.
Steps to reproduce:
1. File > New > Octane Default Startup
2. Add > Mesh > Plane
3. Create New Material for Plane
4. Setup Simple Scatter On Surface Node Network for Plane
5. Setup Octane Mesh Properties
6. Switch viewport to Rendered View. Note the missing scattered objects.
In order to view the scattered objects you must clear the Octane Geo Node field, and reselect "Scatter on surface" while the viewport is in Rendered mode, however this fix is only temporary. Attempting to render a frame doesn't show the scattered objects as well and clearing rendered cache doesn't work.