Yealink Factory Reset
Occasionally, refurbished or used phones may encounter issues with our Device Provisioning - Yealink. When this happens, we recommend performing a factory reset on the phones. For Yealink devices, simply hold down the 'OK' button for 5 seconds, as shown in the graphic below.
And if you’re on the phone itself.
Enter the IP address on your browser (eg 192.168.1.xx).
Username and Password: admin/admin
Settings | Upgrade >> Reset to Factory