vıtalıyırtlach

у вас в компоненте Dialogs передается в props функция sendMessage вы должны ее прокинуть в компонент AddMessageForm :

import React from 'react';
import classes from './Dialogs.module.css';
import DialogItem from "./DialogItem/DialogItem";
import Message from "./Message/Message";
import {Redirect} from "react-router-dom";
import {Field, Form, Formik} from 'formik';

const Dialogs = (props) => {
    let state = props.dialogsPage;

    let dialogsElements = state.dialogs
        .map(el => <DialogItem name={el.name} key={el.id} id={el.id} avatar={el.avatar}/>);
    let messagesElements = state.messages
        .map(el => <Message message={el.message} key={el.id}/>);


    if (!props.isAuth) return <Redirect to={"/login"}/>;

    return (
        <div className={classes.dialogs}>
            <div className={classes.dialogsItems}>
                {dialogsElements}
            </div>
            <div className={classes.messages}>
                <div>{messagesElements}</div>
            </div>
            <AddMessageForm sendMessage={props.sendMessage}/>
        </div>
    )
}



const AddMessageForm = (props) => {
const initialValues = {
    newMessageBody: ''
}
const onSubmit = values => {
    props.sendMessage(values.newMessageBody);
    console.log('запись', values)
}
    return (
        <Formik initialValues={initialValues} onSubmit={onSubmit}>
            <Form>
                <div>
                    <div>
                        <Field as='textarea'
                               id='newMessageBody'
                               name='newMessageBody'/>
                    </div>
                    <button type='submit'>Submit</button>
                </div>
            </Form>
        </Formik>
    )
}

export default Dialogs;