Barnuba,
Fly fishing on rivers and streams in the fall is indeed difficult. There are some exceptions to this but - generally - it's a tough time of year to catch fish. There are several reasons. For one thing, most streams don't have a lot of fish by late October. Streams that were full of stocked trout in the spring and summer simply don't have any (or very few) left due to harvest or, more likely, warm summer water temps. Streams that were full of hungry sunfish and bass during the summer are often barren as fish migrate out with colder temps. And those colder temps can sometimes put the fish off the feed. Finally, there is often a lot of fish movement in the Oct/Nov time period: fish are migrating to deeper water or to spawning areas so they simply aren't where you saw them in spring and summer.
Keep exploring. Focus more on smaller streams with wild trout. Although it's a tough time of year to catch fish, it's also often the best time of year to catch a very large trout or bass and, as several current threads reveal - the trout are often at peak color.