Sometimes, the Remote Desktop client after it loses connection and disconnects cannot reconnect to the same session.
Here at Ibmi Media, as part of our Server Management Services, we regularly help our Customers to fix Windows related errors.
In this context we shall look into the main causes and fixes for this error.

Nature of the error "Remote Desktop client disconnected  and could not connect to the remote computer" ?

As earlier stated, in some cases, after Remote Desktop client loses its connection to the remote desktop, the client cannot immediately reconnect. The user receives one of the following error messages:
Remote Desktop disconnected. Because of a security error, the client could not connect to the remote computer. Verify that you are logged onto the network and then try connecting again.

When the Remote Desktop client reconnects, the RDSH server reconnects the client to a new session instead of the original session.
However, when we check the RDSH server, it says that the original session is still active and did not enter a disconnected state.
A work around for this issue would be to configure keep-alive connection interval policy.

How to fix the error "Remote Desktop client disconnected  and could not connect to the remote computer" ?

We can enable the Configure keep-alive connection interval policy in the Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Connections group policy folder.
Once we enable this policy, we must enter a keep-alive interval. The keep-alive interval determines how often, in minutes, the server checks the session state.
This issue can also be fixed by re-configuring the authentication and configuration settings. We can reconfigure these settings at either the server level or by using group policy objects (GPOs).
Here is how to reconfigure the settings: Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Security group policy folder;
i. On the RD Session Host server, open Remote Desktop Session Host Configuration.
ii. Under Connections, right-click the name of the connection, then select Properties.
iii. In the Properties dialog box for the connection, on the General tab, in Security layer, select a security method.
iv. Go to Encryption level and select the level you want. You can select Low, Client Compatible, High, or FIPS Compliant.

[Need urgent support in fixing Windows errors? – We are available 24*7]