No instance of play.api.libs.json.Format is available for models.AccountStatus in the implicit scope

No instance of play.api.libs.json.Format is available for models.AccountStatus in the implicit scope.

This is the code taken from a github page, and only class names and variable names are changed.

package models

import slick.jdbc.H2Profile._
import play.api.libs.json._

case class Account(id: Long, name: String, category: Int, status:AccountStatus)

object Account {
  implicit val accountFormat = Json.format[Account]
}

sealed abstract class AccountStatus(val as:Int)

object AccountStatus{
  final case object Draft extends AccountStatus(0)
  final case object Active extends AccountStatus(1)
  final case object Blocked extends AccountStatus(2)
  final case object Defaulter extends AccountStatus(3)

  implicit val columnType: BaseColumnType[AccountStatus] = MappedColumnType.base[AccountStatus,Int](AccountStatus.toInt, AccountStatus.fromInt)

  private def toInt(as:AccountStatus):Int = as match {
    case Draft => 0
    case Active => 1
    case Blocked => 2
    case Defaulter => 3
  }

  private def fromInt(as: Int): AccountStatus = as match {
    case 0 => Draft
    case 1 => Active
    case 2 => Blocked
    case 3 => Defaulter
    _ => sys.error("Out of bound AccountStatus Value.")
  }
}

https://github.com/playframework/play-scala-slick-example/blob/2.6.x/app/models/Person.scala