Maybe this will help:

https://www.musictech.net/tutorials/fl-studio-tutorial-midi-1/

Also google/bing MIDI recording in FL will bring up other tutorials.

Mike and I are saying the same thing in that you have to set up the MIDI channels in both your keyboard and FL.

Note that depending on your audio/MIDI interface you can record 16 or more channels simultaneously, but you would need that many different MIDI inputs and players!

Have you tried my original suggestion? That is how I record MIDI, usually one track at a time. If JonD or BobH are here I can record two different MIDI track simultaneously. OR if you can split your keyboard into different zones then you can record 2 or more MIDI tracks with different channels simultaneously.

Here is how record MIDI when I'm alone. Track 1 MIDI channel one I may put down a bass line. Track 2 MIDI channel one I might put down a piano line, etc. Note that because I am using totally different tracks and sounds I can use MIDI channel 1 again as the tracks will not interfere with each other. As Mike indicated MIDI channel 10 is reserved for drums.

I'm in a fitness protection program. I'm been hiding from exercise.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware