US Citizen traveling to Hong Kong but wanting to spend a few days in Shenzhen

I'm a US citizen traveling to Hong Kong in a couple of weeks. I'd like to spend a couple of days in SZ and from what I've read, it looks like I'll be able to get the VOA once I arrive in Hong Kong. However, the China Consulate in Los Angeles told me I need to apply for a China Visa before my trip. Can you confirm that US citizens are eligible for the VOA? I know that's what your article states but I've read a few websites that said US citizens are ineligible. Thank you for your help!