I want to map the knobs/pads/faders to things in ableton, but I click on the MIDI Learn function in Ableton, and move a knob or fader and it doesn't map...
In the settings, Midi tab, you should select "remote" as input for your keyboard's midi channel
Menu "Options", last item "Settings", on the dialog box that opens, you have some tab vertically on the left. Click on "Midi Sync" (3rd from the top).
Then you should see a list of Midi ports. Find the "Input" corresponding to your midi channel/keyboard. on the right hand side, you have 3 buttons (3 columns Track-Sync-Remote), On or OFF, the last on the right must be turned On in order for Ableton Live to accept your Midi Messages for any control learning.
Hope this helps.