package not working

Hello,i will install package but i can’t use it it’s show me many error’s

Uncaught Error: Element ref was specified as a string (inner) but no owner was set. This could happen for one of the following reasons:
1. You may be adding a ref to a functional component
2. You may be adding a ref to a component that was not created inside a component's render method
3. You have multiple copies of React loaded

my component

import React, { Component } from 'react'
import BigCalendar from 'react-big-calendar'
import moment from 'moment'
BigCalendar.setLocalizer(BigCalendar.momentLocalizer(moment))
 
class CalendarDashboardBody extends Component {
    state = {
        fake: [
            {
                id: 0,
                title: 'All Day Event very long title',
                allDay: true,
                start: new Date(2015, 3, 0),
                end: new Date(2015, 3, 1),
              },
              {
                id: 1,
                title: 'Long Event',
                start: new Date(2015, 3, 7),
                end: new Date(2015, 3, 10),
              }
        ]
    }
    render() {
        return (
            <BigCalendar
                events={this.state.fake}
                startAccessor='startDate'
                endAccessor='endDate'
            />
        )
    }
}

export default CalendarDashboardBody

[ZhoraKhachatryanArmweb-zz]

Thanks,i solved it,problem is the, bundle.js in my index.html i have the <script src="/bundle.js"></script> I delete it and it’s working

[jquense]

Make sure you only have one copy of each. Generally bundlers give you hooks for doing that, like alias in webpack