I am having problems with setState - node.js

Question

I'm working on a simple login site and to navigate between Login and Sign up site I made a state called "aktivSide" meaning "activeSite" which is supposed to determine whether the login site or the sign up site will display.
Whenever I click on the "Registrer Bruker" (sign up) button, I get this error message:
Uncaught TypeError: Cannot read properties of undefined (reading 'setState')
import planB from "./plan_b.json"
import logo from './bilder/logo.png'
import './App.css';
import { FontAwesomeIcon } from '#fortawesome/react-fontawesome'
import { faEyeSlash, faEye } from '#fortawesome/free-solid-svg-icons'
import React from 'react';
class App extends React.Component {
//React
constructor(props) {
super(props);
this.state = {
aktivSide: "tom"
};
}
render() {
//JavaScript
return (
//jsx (javascript og HTML)
<>
<div onLoad={() => this.setState({ aktivSide: <LoggInn /> })} className="App">
<title>SpeedType</title>
<header className="App-header">
<div id="topp">
<img id="logoen" width={300} src={logo}></img>
</div>
<button onClick={() => console.log(this.state.aktivSide)}>state</button>
{this.state.aktivSide}
</header>
</div>
</>
)
function RegistrerBruker() {
return (
<>
<h1>Registrer Bruker</h1>
<input type="text" placeholder='brukernavn' className='input_text'></input>
<div className='passord'>
<input type="password" placeholder='passord' className='input_text'></input>
<FontAwesomeIcon className='eye_icon' id='eye_icon1' />
</div>
<p id='passordTekst'>tom</p>
<div className='knapper'>
<button className='knapper_login'><p>Logg Inn</p></button>
<button className='knapper_login'><p>Registrer deg</p></button>
</div>
</>
)
}
function LoggInn() {
//JavaScript
return (
//jsx
<>
<h1>Logg inn</h1>
<input type="text" placeholder='brukernavn' className='input_text'></input>
<div className='passord'>
<input type="password" placeholder='passord' className='input_text'></input>
<FontAwesomeIcon className='eye_icon' id='eye_icon1' />
</div>
<p id='passordTekst'>tom</p>
<div className='knapper'>
<button className='knapper_login'><p>Logg Inn</p></button>
<button onClick={() => this.setState({ aktivSide: <RegistrerBruker /> })} className='knapper_login'><p>Registrer deg</p></button>
</div>
</>
)
}
}
}
export default App;
I've tried adding:
this.aktivSide.bind(this);
to the constructor, but nothing will display.