Upuah
Go to Channels, add a WhatsApp channel, and press Connect. A QR code appears.
On the phone that owns the number, open WhatsApp, go to Linked devices, and scan the code. The status turns to Connected within a few seconds.
Use a number that is not already linked to WhatsApp Business on another desktop session. Keep the phone online and charged: it is the device that actually holds the session.
If the status drops back to Disconnected, open the channel again and scan a fresh code. Nothing in your conversation history is lost.