External contacts are gone after changing mail/account

[ChrisJonkers91]

We are splitting the organisation into 2 different organisations.

We are using a onprem AD with Azure Sync to azure, everything works well with that.

Severel people already have an account like (example) email address removed for privacy reasons

thats needs to be changed to (example) email address removed for privacy reasons

when i change this in onprem AD the sync succesfully changed it in Azure, we are relogging every office application to the new UPN with the new mailaddress but when we search for our external contacts, everything is gone and looks like:

Does anyone know how i can recover this?

[#2]

The data needs to be migrated from the other tenant

[#3]

Well both organization are in the same tenant, within Active Directory Domains and trusts i added multiple UPN Suffixes.
that is the only switch that i made.

The other thing that i can think of is that meaby the SIP was not added in our domain hosting?
sip 5min CNAME sipdir.online.lync.com
_sip._tls 5min SRV 100 1 443 sipdir.online.lync.com.
_sipfederationtls._tcp 5min SRV 100 1 5061 sipfed.online.lync.com.
lyncdiscover 5min CNAME webdir.online.lync.com.