Hello Ahmad Issa,
Because you have already cleared the safe boot flag and verified the core Remote Desktop services, the infrastructure for your connection is operating correctly. The persistent black screen indicates that the Windows logon sequence is either hanging before it can load the graphical user interface or the display driver is failing to render the remote session properly after the recent boot configuration changes.
To resolve this, you must first verify that Windows is instructed to load the correct visual interface by opening the Task Manager with the Ctrl+Shift+Esc shortcut, running a new task, and typing regedit. Navigate through the HKEY_LOCAL_MACHINE hive into Software, Microsoft, Windows NT, CurrentVersion, and select the Winlogon key to ensure the Shell string value is set exactly to explorer.exe. If that registry configuration is already correct, the root cause is almost certainly the advanced graphics driver model failing to initialize the remote display. You can bypass this rendering failure by launching the Local Group Policy Editor through the Task Manager via the gpedit.msc command. Navigate through Computer Configuration, Administrative Templates, Windows Components, Remote Desktop Services, Remote Desktop Session Host, and into the Remote Session Environment folder. Locate the policy named Use WDDM graphics display driver for Remote Desktop Connections and set it to Disabled. This forces Windows to fall back to an older, highly stable display driver model, which bypasses the rendering failures and will allow the desktop to display correctly upon your next connection.
Domic