This issue started up yesterday. I cannot, regardless of font type or size or capitalization, type the letter "h" using the text tool. I can copy and paste the letter in, but trying to type it any other way does nothing.
Assuming that your using the same keyboard to type this post and the H seems to be working, I would try resetting Photoshop's preferences.
How to reset Photoshop preferences (In Windows): First, hold down all three Ctrl + Alt + Shift buttons. Now "while keeping those button held," simply open Photoshop or a file that opens with Photoshop, and as Photoshop loads, you should get a prompt asking if you would like to "delete the Photoshop settings file", Click yes. You should now have a fresh slate with all of the settings returned to their default.
On a Mac, hold Shift + Option + Command while starting Photoshop to delete the preferences.