PayPal 401 Client Authentication Failed in Sandbox environment with node js sdk - node.js

Question

I've followed this guide https://developer.paypal.com/docs/checkout/reference/server-integration/setup-sdk/ and this example https://github.com/paypal/Checkout-Nodejs-SDK/
Here is my code:
import paypalCheckout from '#paypal/checkout-server-sdk';
const environment = new paypalCheckout.core.SandboxEnvironment(
'ACTUAL_CLIENT_ID_FROM_PAYPAL_DASHBOARD',
'ACTUAL_CLIENT_SECRET_FROM_PAYPAL_DASHBOARD'
);
const client = new paypalCheckout.core.PayPalHttpClient(environment);
const request = new paypalCheckout.orders.OrdersCreateRequest();
request.requestBody({
intent: 'CAPTURE',
purchase_units: [
{
amount: {
currency_code: 'USD',
value: `100.00`
}
}
],
});
client.execute(request)
.then((response) => {
console.log(`${JSON.stringify(response)}`);
console.log(`${JSON.stringify(response?.result)}`);
})
.catch((executeError) => {
console.log(`${JSON.stringify(executeError)}`);
});
I get:
{
error: HttpError: {"error":"invalid_client","error_description":"Client Authentication failed"}
at IncomingMessage.<anonymous> (.../node_modules/#paypal/paypalhttp/lib/paypalhttp/http_client.js:136:22)
at IncomingMessage.emit (events.js:388:22)
at endReadableNT (internal/streams/readable.js:1336:12)
at processTicksAndRejections (internal/process/task_queues.js:82:21) {
statusCode: 401,
headers: {
'content-type': 'application/json',
'content-length': '77',
connection: 'close',
date: 'Tue, 29 Jun 2021 01:22:38 GMT',
'cache-control': 'max-age=0, no-cache, no-store, must-revalidate',
'paypal-debug-id': 'c2b.......c7a',
'x-paypal-token-service': 'IAAS',
'strict-transport-security': 'max-age=31536000; includeSubDomains'
},
_originalError: {
text: '{"error":"invalid_client","error_description":"Client Authentication failed"}',
statusCode: 401,
headers: [Object]
}
},
message: '{"error":"invalid_client","error_description":"Client Authentication failed"}'
}
I've searched Google and Stack Overflow but I only find similar issues about switching from sandbox to live.
My code isn't working in sandbox environment.