console says flatMap() isnt a function even though it is

Question

I'm coding a bot with 3 people and there is a random error i can't fix which is super annoying, I keep getting the error 'flatMap() isn't a function' Code:

module.exports = () =>
  getFilenames('../widgets')
    .map(getHandlerFilePath)
    .flatMap(getHandlers)
    .reduce(groupByHandlerName, { ready: [] });