Singapore passport holder VOA for shenzhen from HK

Of course, not. There are no problem in this regard whatsoever. When we talk about the problems, recent feedback talk about very huge crowds of those who apply for this visa and a subsequent very long waiting times. In my opinion, the best way to bypass such a long waiting times would be to take a ferry from Hong Kong to Shekou port in Shenzhen. However, you should be aware of the opening hours at Shekou port: 9:00 - 13:00 & 14:30 - 16:30.