From online photos f that cooker, the timer looks like a normal 5-button timer. The buttons should pull out - maybe with a bit of a twist. Be careful to pull dead straight and not to tip the head.
ONce the button is out, clean off the congealed cooking crud from the shaft - i have often used a bit of kitchen towel sprayed with WD40 fo rthe shaft and WD40 on a cotton bud or a cocktail stick to clear out the hole (Be careful you just clean - don't push stuff in).
Go slowly and carefully
XXX
April 2016