To add to what the others have said, it's not usually so much the fly, but the location, location, location where you cast it. Success with spinning tackle does not always relate to success with fly tackle simply because of differences in the weight of flies compared to lures. However, as Ard has said, the fish will be in the same places regardless of the tackle you choose. The issue is usually getting the fly to where the fish are. Also, as Ard has said, positioning yourself for casting is much more critical with fly tackle, because most folks just getting started with fly tackle can't cast a fly line & the fly similar distances or sometimes with the same accuracy as they can with other tackle.
IMO, all flies will catch some fish, regardless of how pretty or ugly they are or how well they're tied.
Work on improving your tying skills, and subsequently your flies, because that will improve their quality & they will last longer, which will eventually equate to more fish per fly. Tying is also a lot of fun too, so learning the various techniques will expand the enjoyment of tying your own. If you continue to tie proven patterns such as the Woolly Buggers, that should not even be an issue. But, like lures, nothing works all the time.
Also, work on improving your presentation skills, just as you have said you have done with other tackle. Just as with lures, where you cast it, and how you retrieve the lure makes a difference in success. Flies are no different, but do require adjustments from what you've been doing with lures. The adjustments will be such things as sink rates & of course sizes. Flies may not sink as fast as lures you've been using, so you need to allow them longer time to get to the depth required. If you've been using lures of a certain size with success, then flies of similar size might be in order, if the fly rod & line you have will cast that size fly. Fly rods, like spinning or bait casting tackle, are not one size fits all, so don't expect the same types of result. You still have to compare apples to apples.
To further add to what Ard has said, next time you go fishing, concentrate on the fishing & not as much on the catching. This may sound odd, but I found very early in my fly fishing experience, that once I improved my casting & presentations, catching more fish was an added bonus. Eventually, I went to bigger & heavier fly rods & flies, and the size of fish I caught increased. This is not to say that big fish won't eat small flies. But, generally bigger flies entice bigger fish more than smaller flies, particularly species such as bass. I'm primarily a bass & Striped bass angler, which is easier to up size for as far as tackle goes. Trout can be similar, but you do have to do it in a manner that fits the size of the trout in your area. If the waters hold nothing but 6" trout, then 10" streamers are not going to improve your catch rate of trout. It might however improve you chances with bigger bass, but only if you have the equipment to handle such a big fly.