I am new to blender and trying to use edit mode and circle selection in order to separate parts of a mesh so the separate parts are small for import into Roblox. I have my mesh cantered and edit mode activated and pressed C and selected a section from the centre of the mesh which showed up as selected but when I then press P for separation nothing shows. I took a screenshot.
Until a tool has 'finished', you can't start a new one. In the case of the Circle Select tool this means either pressing Enter to 'Confirm' the tool, or Esc or Right-Click to 'Cancel' the tool (though in this case cancelling doesn't actually 'undo' the selection you made, it just ends it).