When a Zero touch provisioned device is created on the Kwebbl panel, the system sends unique link to the Yealink redirection service. After factory reset the device goes to the Yealink service, receives the unique link to our system and then receives all the settings from us.

Yealink keeps these links only for 14 days. This means if you make a factory reset to a device that is auto provisioned longer than two weeks, you need to edit the device in the panel to refresh the link. 

Editing the device in the panel followed by factory reset will force a new unique link in the Yealink redirection service after which the device will register and provision again.