In a Microsoft Skype for Business Server 2019 environment, consider the following scenario:
A PSTN user calls a call queue number and the call is answered by a Skype for Business Online agent.
The agent tries to transfer the call to another internal Skype for Business Online user who’s from different SIP domain.
In this scenario, the call transfer fails. The call transfer should work because both users are from same organization even though they are in different sip domains.
To fix this issue, install the September 2019 cumulative update 7.0.2046.143 for Skype for Business Server 2019, Mediation Server.