Can I get a VOA for e.g. Shenzhen or Zhuhai if I already have a proper visa for China for 30 days?

Hi Folks,
I am wondering if i can a VOA for e.g. Shenzhen or Zhuhai from Hong Kong if I already have a proper entry permit for China for 30 days for a later trip planned? (German citizenship and HK resident)

Thanks for your help!