If the buttons are visible but do nothing, the remote computer's security policy is likely blocking the signal. This is common on Windows 10/11 and Windows Server.
Back up your registry before making changes.
Train all remote users to use Ctrl+Alt+F12 inside the Radmin window to send the secure attention sequence to the remote machine. If customization is needed for corporate environment, pre-configure Radmin Viewer hotkeys via deployment scripts or registry.