Hybrid setup - Unknown presence when migrated back to on-premise

Hi all,

I have a client with a Skype for Business Hybrid setup.  Most users have been migrated to On-Line but to take advantage of PSTN features, some users require to be on-premise.  

When migrating a test user back to on-premise, the user is able to see contacts and presence.  After logging off and back on, it comes up as unknown.

I followed this article http://www.open-a-socket.com/index.php/2017/09/16/how-to-suppress-skype-for-business-attribute-synchronisation-in-aad-connect/ to suppress AD Sync Attributes but the issue still persists.

There is something in AAD Connect sync that changes config but I have exhausted everything. 

Any ideas as to what to look at?

San-J