Nutty,
Welcome. Don't be a stranger here, join in. I'm glad to hear from another carp devotee. Okie's advice is good. Pay attention to what he says. I've seen him carp fish and he's got it down.
Here are a few things I'd consider:
1. What are the fish doing when you're casting to them? Are they cruising? If yes, they can be really hard to catch. You may want to leave that fish and look for another. Cruising fish may not be feeding fish. Look for fish actively feeding. That will up your odds. Also, a fish lying motionless may not be willing to bite. Fish are just like us. They don't feed 24/7. Many fishermen have the mistaken belief that they can catch any fish they see. Wrong. Like you, if you just had a big meal, you're not likely to want to eat again for awhile. Which leads me to my second point.
2. Consider what time of day you're fishing. You need to be there when they're eating and not when they're cruising or resting. In the Summer that's usually early and late. Just because you can see them doesn't mean you can catch them. They've got to be "in the mood".
3. What are they feeding on? Bugs? Bugs on the bottom? Bugs on the top? Or, are they sucking on cattails and gleaning the moss off them. Or maybe they're eating cotton wood seeds. They are very selective as to the size of fly and as to the location. If they're sucking on moss, you'll have a tough time but it can be done. Tie a moss fly with olive marabou or olive dubbing and dap the fly in front of the carps nose. If you'll get on your knees or your butt and creep up on them really slow and not throw a shadow on them, you can get right on top of them. Another trick, as Okie said is to just let the fly lay on the bottom. Sometimes I'll cast and cast to a carp and he'll ignore my fly but if you cast it past him and strip it by and let it fall, he'll ease over and examine it, tip up, and suck it in. If he doesn't, barely twitch it and he'll often pounce on it. Man, I get chills just thinking about this! I can't wait to get started again. They've got such varied personalities. Just like cats.
I went about 2 weeks ago. The water is still really cold and they were feeding on moss. No bugs yet. I probably cast to 20 fish and caught one. I think it's just too cold still. Which leads me to my third point.
3. Time of year. When are you fishing? Winter is tough fishing for most WW species. Spring spawn can be tough too. They've got other things on their minds.
4.Consider the size of fly you use. Sometimes they want a really small fly. Like a size 16 or so.
5. What is the clarity of the water? I've not had much luck fishing for tailing carp in muddy water. They have trouble seeing the fly and I have trouble seeing the take. They normally have a really subtle take and if I don't see them take the fly I usually don't feel it.
6. Try dapping (mentioned earlier). Some days that's the only way I can get one to take. Just dangling the fly right in front of their noses. Again, if you'll get down on your butt and knees and bend over at the waiste making a very small profile and barely creep along, you can get right up on them. I bought a pair of knee pads that basketball players wear that I put over my waders to save my knees and waders. Yeah, I'm serious about my carpin'.
7. Be stealthy. Carp often feed in pods and if you spook one, you'll spook the whole pod. Fish the one nearest deep water first. They'll usually spook to deep water and if you spook him, he may not spook the ones closer to shore.
8.Buy and read "Carp on the Fly" by Reynolds, Befus, and Berryman. It's not the "Bible" but, as far as I know, it's the best how to carp fishin' book on the market.

Good luck. I love fishing for carp.