The indefinite pronoun none can be either singular (e.g., “There is none left”) or plural (e.g., “None of the books have been read”).
Some sources argue that none should always be treated as singular, even when it refers to countable quantities (e.g., “None of the books has been read”). This is based on the idea that it is short for “not one” and thus logically must be singular.
But in fact, none can also mean “not any,” and it has been used as both singular and plural for centuries. There’s no good reason to restrict it to the singular form. We recommend using whichever form reads most naturally in the context.