Is there any chance of getting birds to come to my feeder

I've just bought a window feeder for the window of a first floor flat. We are in a leafy city suburb and there are lots of old roofs/chimneys, big grassy gardens and high leafy trees around us. We get lots of woodpigeons, collared doves and magpies, and fewer blackbirds and bluetits though I have seen them. The bluetits in particular seem to pass by our house a lot as if passing between their nests and their preferred feeding places. I saw one stop on our feeder once but due to the quality of the food there (by that point I had actually given up on a bird ever visiting) it left straight away. I am now putting in a new suet ball every week but nothing comes. I've put a few oats, seeds, cheese, etc around the suet ball too. I've left the curtains closed during the day for two weeks running now as we are out at work anyway, as some people said they won't approach a new window when they can see the room inside, but still none of my suet balls have been nibbled. Is there anything I can do? Although there are a lot of gardens around us, we don't have one ourselves, and I'm desperate to have a little birdspotting cheer in my winter as I can't get out for walks as much in the winter :( Any advice appreciated.