Request a runway change is only available after you receive taxi or landing instructions giving you the assigned runway. You did not try C\S\W at those times but were attempting to do so mid-flight, in which case the hotkey's mode is then to request 'warp' to a given waypoint.
I also noticed you disregarded ATC instructions to descend and maintain FL 190 and just continued descending... not only is that bad practice it also renders you likely to have problems in your approach... just thought I'd mention that in passing
