I agree with Tim. You need reasonably dark skies (visual limiting magnitude at the zenith at least to 5th magnitude) for most nebulae ,and clusters are even easier to detect in slightly worse skies. Of course, trying to detect them low in the sky (more than 40 degrees from the zenith) will greatly increase the chances of failure.
I assume you are pointing the scope at the right spot (if using a go-to, is it aligned properly?) and can't detect these objects. If so, it's light pollution keeping them from being seen. If you are only a tiny bit off in positioning, you won't see the object in most cases.
In the next couple of weeks the Moon will be rising late enough to allow you to try for some objects that are nearly overhead (in Hercules, Lyra, Cygnus and later on Perseus and Andromeda) despite your light pollution, if it's not too severe. Don't give up and keep trying. Locating objects in the sky takes a while to master, especially in light polluted skies.
Mr Q