Skype telephone not receiving calls on Hub One

[#1]

We have been using a Skype telephone on PlusNet regular Broadband with a Technicolor router for years with no problems. The telephone was plugged into a LAN socket on the Technicolor router.

We have just upgraded to Plusnet Fibre broadband with a Hub One router. The telephone is once again plugged into a LAN socket. We are able to make calls on the telephone but not receive them. The phone is shown as connected on the hub manager. Regular Skype on the PC works fine.

Any ideas as to why we cannot receive calls please?

[#2]

Are you getting alerted to incoming calls but the handset isn't allowing you to hear them?

[#3]

No, when we call the Skype telephone number the calling phone has the usual ringtone but nothing happens on the receiving Skype phone. Making calls on the Skype phone through Hub One is fine, its seems we simply have one way rather than two way communication with the hub.

[#4]

It's not related to this is it https://www.theregister.co.uk/2017/06/09/microsoft_pulls_plug_on_skype_phones/