In the event that any (or all) Ekran System Clients are displayed as being offline on the Client Management page, this may be for many possible reasons, but the main issues (i.e. causes) and possible solutions are as follows:
The Client was uninstalled from an endpoint computer, but its data is still displayed in the system.
The Client also needs to be deleted in the Management Tool (after uninstalling it using either a remote or local method of uninstallation), after which the Client will no longer be displayed in the Management Tool, and all data associated with the Client is deleted.
Isolation mode was enabled on the Ekran System Application Server.
The computer where the Ekran System Client is installed is turned off.
Turn the Client computer on.
There is a network issue (i.e. no connection) between the Client and the Application Server.
The network problems need to be fixed.
The port for communication between the Client and the Application Server machines is blocked by a software firewall or hardware firewall.
Either disable the firewall, or allow it to open the connection port (which by default is 9447).
The EkranClient service is stopped, or does not start automatically on the endpoint machine.
Start the EkranClient service manually, and check that all the required files are located in the Ekran Client root folder (i.e. the folder where the Ekran System Client application is installed), or otherwise reinstall the Client.
The Ekran System Application Server machine has a new IP address / hostname or port, and all the Clients are trying to connect to the Application Server using the old settings.
Either re-install all the Clients using a remote or local method of installation, or modify their settings in the appropriate files (see Points 3-5).