Intellij Idea highlighting error (scala, cats 0.4.1)

CatsApplicative_problem.scala

import cats.data.Validated.{invalid, valid}
import cats.std.all._
import cats.syntax.cartesian._
  
object Boot extends App {
  val a = (valid[String, String]("event 1 ok") |@| // does not recognise `|@|` - applicative combine syntax
    invalid[String, String]("event 2 failed!") |@|
    invalid[String, String]("event 3 failed!")) map {_ + _ + _}
    
  println(a)
}