The word none can be singular or plural, depending on the number of the noun it is referring to. Back in my 4th grade English class, none was always singular. Again, grammar rules have changed and modern thought is that it can be either singular or plural. One way to decide is when you can use not one, then none is singular. If you mean not any, then none is plural.
- None of the directions he gave to get to the grocery store is accurate (meaning that not one of the different directions he gave to get to the grocery store is accurate)
- None of the directions he gave are accurate (meaning that not any of the directions he has ever given are accurate)
Confused yet? How about these:
- None of his electronic devices is set up correctly (not one of his devices)
- Of all his electronic devices, none are using Wi-Fi (not any of his devices)
Whether you use is or are will let your reader know what you mean. By saying “None of his electronic devices is set up correctly,” your reader should understand that you mean that not one of his many devices is set up correctly. When you say “Of all his electronic devices, none are using Wi-Fi,” your reader understands that you mean that not any of his many devices are using Wi-Fi. The difference is relatively minor and regardless of which way you use it, some people (who learned that none was always singular back in 4th grade) will try to correct you. Know that as long as you are comfortable that you are using it correctly for what you mean, you can treat them like your mother-in-law—smile, nod your head, and keep doing it your way.