By default a Windows Server allows two (2) simultaneous remote desktop sessions, if you want to allow more than 2 simultaneous remote desktop sessions on your server, you will need to configure a Remote Desktop Services (RDS) deployment with appropriate RDS client access licenses (CALs).
Welcome to Remote Desktop Services
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/welcome-to-rds
License your RDS deployment with client access licenses (CALs)
https://learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-client-access-license
For example, if you need more than two (2) connections to your Windows Server 2019 from internal device, then, below RDS serve role might be necessary:
1. Remote Desktop Connection Broker.
2. Remote Desktop Session Host.
3. Remote Desktop Licensing server – there is 120-day licensing grace period, appropriate RDS CALs should be purchased and installed before it has expired.
You can install all the server roles on single server system and using session-based quick deployment.
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Leon