Troubleshooting WhatsApp Cloud API Delivery Issue

I'm facing an issue with the Facebook WhatsApp Cloud API. Despite receiving a success message from the API, my WhatsApp messages are not being delivered to the recipient.

Here are the details:
1. I'm using the WhatsApp Business API to send messages.
2. I've verified that the recipient's phone number is correct.
3. I'm using the following API endpoint and payload:

API_VERSION = 'v21.0'
URL = f'https://graph.facebook.com/{API_VERSION}/{PHONE_NUMBER_ID}/messages'

Headers:
{
'Authorization': f'Bearer {ACCESS_TOKEN}',
'Content-Type': 'application/json'
}

Payload:
{
"messaging_product": "whatsapp",
"to": RECIPIENT_PHONE_NUMBER,
"type": "text",
"text": {
"body": "Hello, this is a test message from the WhatsApp Business API!"
}
}

I'm receiving a 200 status code and a success message from the API, but the message is not being delivered to the recipient.

Could you please assist me in resolving this issue?