REMOTE DESKTOP CONNECTION ERROR, AFTER 2 ACTIVE SESSIONS

Good day All,
The other day when i was working a colleague of mine pulled me and showed me a Server when tried to RDP was showing the below error...

So he started to ping  and there was ping response and he even tried with file share and it was working fine too.. So he determined that Server is online.. so he logged on to Server via ILO and he saw server is health and online..So he used the console and logged in..

He poked around could't find any problem still he was not able to RDP to server.. so he disconnected all the RDP sessions which were active and disconnected state and boom RDP started to work...
now that puzzled me too why after disconnecting sessions we were able to RDP ??????

Well now i had to replicate the issue .. So i took 2 RDP Session to same server and when i tried the 3 RDP session boom i got the same error, usually if you try a 3 rd session it should still open a connection and pop us with message saying if you want to disconnect any active user session, but this is strange as it was not going that far just failing with error "THIS COMPUTER CAN'T CONNECT TO THE REMOTE COMPUTER"

So first thing i opened was Remote desktop Host configuration mmc..  and checked the connections properties..

well i did't notice anything strange so next thing was checking the local group policy and local security policy and that was looking good too..
So i power on my lab VM and started to check the connection settings.. it was all the same.. so i said let me delete the RDP listener and re-create it again.. so I deleted the RDP-Tcp connection on my lab VM and started the new connection wizard..

So when i came to this option i kind of stopped and said wait a mint let me check something on the registry...

So browsed to below path in registry

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp

MaxInstanceCount=dword::00000002

strange.. so looks like some one when creating the listener instead of choosing concurrent "Unlimited connections"  selected the connections to 2 which was restricting any connections more than 2 sessions..


So changed the registry settings as below and that fixed the issue...

MaxInstanceCount=dword:ffffffff   - unlimited current connections



Hope this helps someone... thanks for reading through.. and have a good day...