Due to changes introduced by Yealink in 2020, some phones if factory reset will require the user to enter the last 5 digits of the Serial Number into the phone before it will complete the provisioning procedure.
1. Locate the Serial Number
Turn over the phone and locate the serial number label above the MAC label. The labels are below the two Ethernet ports labelled "PC and Internet".
If you are missing the labels, please contact URL Networks Support.