As someone that recruits virtual assistants I deal with this almost daily.
I tell people all the time that working in a brick and mortar office for 30 years does not qualify them to be a virtual assistant. It is a transition and you have to have excellent communication skills to switch from "in person" to "virtual". Some people just can't do it.
You also have to have excellent computer skills and be able to find answers to your own questions, because there is not always someone to ask.
So.. in a nutshell, you don't need a fancy degree or a certification from some expensive course.. you need great communication skills, you need to be extremely internet savvy, and you have to be resourceful and be able to research.
Hope that helps!