HI MilevValeri-3184,
1.Are W2019 RD licensing server and w2012 RD session host server in the same AD domain ?
2.Please make sure we have enrolled w2019 remote desktop per user CAL on w2019 RD licensing server successfully first like below picture.
3.We can try to enter gpedit.msc in CMD on w2012 session host server, then remove old w2012 rdls server and specify your w2019 rdls server directly. After that, we can remote access w2012 RD session host server by using domain user account.
Computer Configuration - Policies - Administrative Templates - Windows Components - Remote Desktop Services - Remote Desktop Session Host - Licensing
use the specified remote desktop license servers enable
specify your rdls server w2019 rdls server
set the remote desktop licensing mode enable per user
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