From Level 36 onwards in Candy Crush Saga you can encounter "locked" candy ...
These are normal sweets but are initially "locked" in place by
strands of liquorice and can't be swapped with
and won't move, fall etc .
This includes a no-valid-moves "shuffle" which will not move
They can only be unlocked by making a match with the "trapped" candy. ...
So (in the pic) swapping the green and red (in the green box) will NOT free up any locked candy.
However making the orange swap (in the white box) will unlock the locked orange - which will remain.
So you'll need to match it AGAIN to get rid of it.
Note, in this example the two lines of locked candies are holding back the chocolate which can't expand further as it can't spread to locked candy.
Therefore the FIRST one you unlock will immediately get swallowed up by a piece of chocolate as it "escapes" and then slowly spreads over the board as you play your moves.
Thus on this sort of level you may wish to keep the chocolate confined for as long as possible.
Triggering "specials," eg. a striped candy "blast," will blast through ALL locked candies in it's path, unlocking all the candies, but leaving them in place.