A guitar question ..plee?

hello.....anyways i have a cheap guitar i got about a month ago anyways whenever i play a chord where all the strings are covered or a barre chord it doesnt ring it's just flat but when i try to see what's wrong and play them individually they ring clearly..and i do press down hard enough .. i'm sorta a newb so ..is it because my cheap guitar has really cheapo strings or is it something else??