Hi tedr, welcome to the forum!
First, are you sure the PE has finished booting/installing? It can take quite a while.
Second, you might want to read through a few of the following threads to see what other updaters have encountered:
https://www.mobileread.com/forums/sho...d.php?t=134237
https://www.mobileread.com/forums/sho...d.php?t=132878
These are long posts, and the origins can be outdated -- you might want to start at the end.
Edit: Well darn!
Luckily for you, Obsessed beat me to it, with more and better help!
There's more info available if you need it. Let us know!