Why is my Microsoft Pinyin IME suddenly making traditional characters instead of simplified?
The Simplified Chinese Microsoft Pinyin IME is capable of both simplified and traditional characters. When you install it, it will be set for simplified characters. It is set up to toggle between simplified and traditional with the keybinding ctrlshiftF. It is easy to do this accidentally if the IME is active and you do a "Find All" in Visual Studio or a similar program with the same keybinding.

You can toggle back by activating the IME (if necessary, using WinSpace) and then toggling back with ctrlshiftF.

You can disable this key or change it to another letter (note, ctrlshift is not optional!) by navigating to the keyboard options:


Press WinS and start typing "language" and select:





Click on the language and it will expand and offer an "options" button:





Now find the keyboards, click on the "Microsoft Pinyin" keyboard (probably the only one):





From there you can toggle back to simplified under "General" and modify the toggle binding at the bottom of "Keys"