Press Ctrl+Alt+Del inside a Remote Desktop session and Task Manager opens on your own computer, not the remote one. Windows intercepts that combination locally before the session ever sees it, and it always will.
Here is what to press instead.
The shortcut that works
Ctrl+Shift+Esc opens Task Manager directly on the remote machine. This is the fastest way, and it works whether the session is windowed or full screen.
If you want the security screen
Ctrl+Alt+End is the Remote Desktop equivalent of Ctrl+Alt+Del. It sends the security screen to the remote session, and Task Manager is one of the options on it. Use this one when you also want Lock, Sign out or Change a password.
Three other ways in
If the keyboard shortcuts are intercepted by something else, or you are on a client that does not pass them through:
- Right-click the taskbar in the remote session and choose Task Manager.
- Press Win+R, type
taskmgrand press Enter. - Open the Start menu in the session and type Task Manager.
All three run inside the session, so they hit the remote machine.
What you will and will not see
Task Manager inside an RDP session shows that one machine, and only what your account has rights to see. Without administrative rights on the server, the Users and Details tabs will not show you other people's sessions or processes.
That is fine when you are troubleshooting the server you are already connected to. It stops being fine when the question is "which of my six session hosts is the one with the problem", because Task Manager will not tell you. It has no idea the other five exist.
When one server is not the question
On a Remote Desktop Services deployment the useful view is across servers, not inside one of them. Who is signed in where, and whose session is eating the CPU.
Terminal Services Manager shows the sessions, users and processes of several RDS servers in a single window, without connecting to each one. From the same list you can end a process, log off a session, or shadow (remote control) a user.
Related reading: how to see who is logged on to a Remote Desktop server, and how to find which user is using high CPU on an RDS host.