Hey!
These are all files I updated in the very latest update to fix a big where text wouldn't cast a shadow, and to add more masking options to UI text.
Please do a back up before updating just in case, but have you tried setting Unity's asset serialization mode to "Force Text"? Or have you tried deleting the original files before importing the new ones? If the GUIs are different, it might just be that you have to re-apply the shaders in STM's inspector. (Changing any value will tell the mesh to Rebuild, which might be why it's not showing?
Also, if you moved STM's files to a different folder, this might also cause the issue as Unity will always place new files in the original folder, so that would create a double instead of replacing the original.
There's a bunch of things that could be causing this, but these are the first solutions I can think of off the top of my head! Please let me know what works for you.
-Kai