Re: dry fly presentation?
Don't beat yourself up too badly, that part of the river gets pounded, even more so now that the Green Drakes started a few days ago. Fish become wary and have seen many a fly, so fishing gets tougher. This is all part of your learning.
I agree with the thought from above that if you don't see fish actively rising, then stay with a nymph (or even an emerger fished down in the water column). And once you do see fish rising you have to decide if they are eating emergers just under/or in the surface film or if they are eating adults? OR something all together different. Once you have made a decision....fish to the fish, don't cast randomly in hopes of catching the odd fish unless you just want casting practice.
You didn't mention what flies you tried?
*Comments posted above are only my opinion. I may be right....eh, I'm probably wrong. Take 'em for what they're worth.*