I'm bemused by this and could do with any light you can shine on this.
So I want to add text to an existing note, so I select the note. (i can double click it to open in a new window, or just select it so that it opens in the viewing pane)
I then click into the note where I want to insert text, and I can see the cursor flashing there.
I start typing and no input appears on the screen, in fact the cursor disappears.
I then re-select the window, see the prompt again and when I start typing the text appears.
This happens reliably.
I tried double clicking in the note and pausing before typing but the only way I've found to proceed at present is to start tying and then re-select the note.
I may have observed something similar when trying to copy and paste (ie I have to select and copy twice before I can paste) but I'm not sure of this.
Windows184.108.40.20627 (307027) Public (CE Build ce-43.0.4829)
As you can imagine this is a little frustrating.