Hi PJ!
Welcome to the wonderful world of the Pocket eDGe!!
I suspect the problem is that you have to open the journal and/or the reader from the tablet side before you can switch between them. Once you have opened both you should be able to use the button to switch back and forth.
I have never tried having all 3 applications open at once and switching. I think I'll see if that works!
Have fun exploring, and ask any questions you have. I found the PE slow to learn but easy to use once I learned how.
Enjoy!!