Phonebook not working on Yealink devices after upgrade to V20

[Beuningen IT]

I've slowly started to upgrade customers' servers from V18 to V20. However, one of my customers is complaining that their 3CX Phonebook on Yealink hardphones isn't working anymore. They're using a mix of T53, T57 and W60B's in their office. When you open the phonebook it first says "Cannot download remote phonebook!" and after you press Back the list is empty (saying "None"). I've rebooted the server, checked if everything was up-to-date (which it is, including the phones firmwares).

 

[Alphabetic]

I would remove a phone from an ext and add it back to send the RPS. Factory reset the phone and see if it works then. It could be pointing to old URL with :5001

 

[SweetAction]

What SSL cert (custom or 3CX LetsEncrypt)?

Make sure the phone trusts the cert from the PBX.