At a guess, Its most likely either of 2 things and probably the second.
1. You havent reassembled it properly
This is very easy to do and not brilliantly explained in the manual.
I dont have mine to check anymore, but the upper burr needed to be reinserted ONLY when the collar was fully anti-clockwise....ie the pointer was lined up with at the release button. If this is not done, the burr wont travel up and down within the thread as the collar is rotated.
2. Arrow alignment.
When you reinsert the burrs you must line up to those little arrows painted on th e stator.
There are actually two arrows [180 deg apart].
The grind setting is influenced by which arrow you align up to.
From memory, I found with mine, that depending on which arrow I used, the espresso range was either around 13-16 or 6-8.
All grinders need to be regularily pulled apart for cleaning, you just have to get used to its quirks.
Good luck and let us know how you go.