In tablet mode, once you close touch screen keyboard with X button on right top corner, you will not be able to re-open it again, even using "TouchScreenKeyboard.Open" function.

Workaround: switch to "desktop mode" from "tablet mode", open touchscreen keyboard from taskbar menu, switch back to "tablet mode". Now touchscreen keyboard opens until you close it with X button.

Repro steps:
1. open project "wsa_keyboard.zip".
2. build it to UWP platform.
3. deploy generated solution to Surface 3 tablet set to "tablet mode".
4. press "open keyboard" button. Close keyboard using X button at right top corner. Try to re-open touchscreen keyboard.