Windows 11 no longer has a dedicated "Tablet Mode" toggle. Instead, when the Type Cover is removed, the device automatically switches to a touch-friendly UI based on hardware detection. So, the fix steps differ slightly between Windows 10 and Windows 11.
If you are using Windows 11: Go to Settings → Time & Language → Typing → Touch keyboard and set the dropdown to "When no keyboard attached" (or "Always" if you want it to always appear).
Starting with Windows 11 build 22621.1928, Microsoft replaced the old checkbox with a dropdown menu offering three options: Never, when no keyboard attached, and Always.
If the keyboard cover is still attached, Windows may not detect tablet mode properly. Fully detach or fold back the Type Cover, then test tapping a text box again.
Right-click the Taskbar → select "Show touch keyboard button" (Windows 10) or go to Settings → Personalization → Taskbar → System tray icons → Touch keyboard → On