Pin Authentication option missing

[Evan_Yealink]

Hi Tony, how are you today?

This is Evan from Yealink Support Team, nice to know you here!

During startup, the phone can download a private CA root security certificate used by Skype for Business and obtain the Skype for Business server address by detecting the DHCP options 43.
As a result, you can sign into Skype for Business on your phone with your PIN Authentication credentials. If the DHCP Option 43 is not configured in your network, your phone will not support PIN Authentication sign-in method.

Please check with your IT guys, to see if the DHCP option 43 is congifured or not?

Please let me know if any updates.

Best Regards,
Evan You