Stillwater trout are often highly pressured. Every day they’ll see hundreds and hundreds of flies zipping past them at a variety of speeds. This can make them wary and although they’ll often follow your fly, getting them to take it isn’t always as easy as it might first appear.
Varying the retrieve speed you use – both on different retrieves and within the same retrieve can make all the difference. Don’t just keep doing one-foot strips at the same speed all day or figure-eight retrieve on every cast.
Try some really slow retrieves, try short stop retrieve, try some normal strip retrieves, try roly polying at breakneck speed, and see if you get a hit personally I am not a big fan of the roly-poly but each to their own I say. Add pauses to your retrieve and stop for a second or two to let your fly drop before recommencing. You’ll almost certainly get extra pulls as a result.