I'll help you figure this out. What version of Photoshop & the operating system are you working on?
If you're on Windows, you can use the On-screen keyboard (search in the Window button) to check if the input is getting registered when you type Y in Photoshop & use the On-screen keyboard to type if needed.
Have you tried changing the Font? As a test, reset the Type Tool from the Tool menubar.
Let me know if this helps. Thanks!