Is it normal in Germany for colleagues to not say hello back when you say hello to them?

Been working in a new company in Berlin a while now. The colleagues on my team are mostly friendly, but others who I work with occasionally or ones I've even had personal conversations with don't say hello back to me when I pass them in the hallway..

I normally smile and say 'Hallo' or 'Guten Morgen' only to be looked like with a blank face..

Is this normal? Could be a culture thing, but where I come from its highly impolite..