É necessario fazer a alteração da dll "c:\windows\system32\termsrv.dll", encontrar a seguinte linha e substituir os valores conforme a bild do seu windows 10. 

Programa para editar DLL, HxD - Freeware Hex Editor: https://mh-nexus.de/en/hxd/ 

No programa utilizar a aba Find "Hex-Values"

Windows 10 Version 1903 (updated v2)

Find:

39 81 3C 06 00 00 0F 84 5D 61 01 00

Replace With:

B8 00 01 00 00 89 81 38 06 00 00 90

Windows 10 Version 1809 (updated)

Find:

39 81 3C 06 00 00 0F 84 7F 2C 01 00

Replace With:

B8 00 01 00 00 89 81 38 06 00 00 90

Windows 10 Version 1809

Find:

39 81 3C 06 00 00 0F 84 7F 2C 01 00

Replace With:

B8 00 01 00 00 89 81 38 06 00 00 90

Windows 10 Version 1803

Find:

8B 99 3C 06 00 00 8B B9 38 06 00 00

Replace with:

B8 00 01 00 00 89 81 38 06 00 00 90

Windows 10 Version 1709

Find:

39 81 3C 06 00 00 0F 84 B1 7D 02 00

Replace with:

B8 00 01 00 00 89 81 38 06 00 00 90

Windows 10 Threshold Wave 2 Update

Find:
39 81 3C 06 00 00 0F 84 3F 42 02 00

Replace with:
B8 00 01 00 00 89 81 38 06 00 00 90

Windows 10 RTM 2015

Find:
39 81 3C 06 00 00 0F 84 73 42 02 00

Replace with:
B8 00 01 00 00 89 81 38 06 00 00 90

Fonte tutorial: https://udhyantimilsina.com/2018/07/26/enable-terminal-server-multiple-rdp-sessions-on-windows-10/