As a pronoun, none means (1) not any, (2) not one, (3) not any such thing or person, and (4) no part.
Overzealous proofreaders may want to keep the verb associated with none singular, basing their thinking on the derivation of none from Old English “not one.” But the universal view among grammarians today is that none can be either singular or plural, depending on what you mean in your sentence.
Determine your verb by considering the noun that follows of in the phrase introduced by none: if the noun is singular, make the verb singular. If the noun is plural, base your choice on whether you would be more inclined to use not one (singular) or not any (plural) after none.
- None of the jobs have [or has] been completed yet. (The choice here hinges on whether the intended meaning of the sentence is better served by not one of the jobs [singular] or not any of the jobs [plural].)
- None of the water skiers has arrived at the lake yet. (Intended meaning: Not one of the water skiers has arrived yet.)
- None of the water skiers have arrived at the lake yet. (Intended meaning: Not any of the water skiers have arrived.)
Source: ‘Grammar for Smart People’ by Barry Tarshis.