MacBook Pro's Trackpad stops working when connecting an external keyboard
It's possible that plugging in the keyboard is causing macOS to detect a cursor control device (mouse).

Go to System Preferences app → Accessibility → Mouse &amp; Trackpad and check if Ignore built-in trackpad when mouse or wireless trackpad is present is checked?



If it is, simply uncheck and try again. You should now be able to use the built-in Trackpad normally while your keyboard is plugged in.