If you try to create an Exchange distribution list or a regular security group object in Microsoft Skype for Business Server 2019, the following error event is logged in the Lync Server User Replicator log (on running Debug-CsAddressBookReplication -AnalyzeFailures):
Error code: 547, First occurred: 11:45:40, Last occurred: 12:05:07, Severity: 16, Count: 157, Stored procedure name: RtcSetAbEntry, Text: [# [Microsoft][SQL Server Native Client 11.0][SQL Server]The INSERT statement conflicted with the CHECK constraint "CK__Pool__Fqdn__74AE54BC". The conflict occurred in database "rtcab", table "dbo.Pool", column 'Fqdn'. #][# [Microsoft][SQL Server Native Cl"
To fix this issue, install the December 2021 cumulative update 6 for Skype for Business Server 2019, Core Components.