Can not connect Remote Desktop to windows server after few days

I have a server using Windows Server 2008 R2 SP1, it has been good working some years, but recently there was a problem, other computers can not connect to its remote desktop, the prompt messagebox content is as follows:

1. Remote access to the server is not enabled
2. The remote computer is turned off
3. The remote computer is not available on the network

If restart the server, you can connect, but after a day or so, it won’t work again. If try to stop the Remote Desktop Services service at this time, it will definitely freeze to stop. and if call qwinsta command, it will freeze too.

In addition, I found such this log, I don’t know if it matters:

RDPClient_TCP: An error was encountered when transitioning from TcpStateConnectingTransport to TcpStateDisconnected in response to 2 (error code 0x80004004).

Please help, thanks.